IMPORT: slz: import slz into the tree

SLZ is rarely packaged by distros and there have been complaints about
the CPU and memory usage of ZLIB, leading to some suggestions to better
address the issue by simply integrating SLZ into the tree (just 3 files).
See discussions below:

   https://www.mail-archive.com/haproxy@formilux.org/msg38037.html
   https://www.mail-archive.com/haproxy@formilux.org/msg40079.html
   https://www.mail-archive.com/haproxy@formilux.org/msg40365.html

This patch does just this, after minor adjustments to these files:
  - tables.h was renamed to slz-tables.h
  - tables.h had the precomputed tables removed since not used here
  - slz.c uses includes <import/slz*> instead of "slz*.h"

The slz commit imported here was b06c172 ("slz: avoid a build warning
with -Wimplicit-fallthrough"). No other change was performed either to
SLZ nor to haproxy at this point so that this operation may be replicated
if needed for a future version.
diff --git a/include/import/slz-tables.h b/include/import/slz-tables.h
new file mode 100644
index 0000000..ff6c939
--- /dev/null
+++ b/include/import/slz-tables.h
@@ -0,0 +1,235 @@
+/* Fixed Huffman table as per RFC1951.
+ *
+ *       Lit Value    Bits        Codes
+ *       ---------    ----        -----
+ *         0 - 143     8          00110000 through  10111111
+ *       144 - 255     9         110010000 through 111111111
+ *       256 - 279     7           0000000 through   0010111
+ *       280 - 287     8          11000000 through  11000111
+ *
+ * The codes are encoded in reverse, the high bit of the code appears encoded
+ * as bit 0. The table is built by mkhuff.sh. The 16 bits are encoded this way :
+ *  - bits 0..3  : bits
+ *  - bits 4..12 : code
+ */
+static const uint16_t fixed_huff[288] = {
+	0x00c8, 0x08c8, 0x04c8, 0x0cc8, 0x02c8, 0x0ac8, 0x06c8, 0x0ec8, //   0
+	0x01c8, 0x09c8, 0x05c8, 0x0dc8, 0x03c8, 0x0bc8, 0x07c8, 0x0fc8, //   8
+	0x0028, 0x0828, 0x0428, 0x0c28, 0x0228, 0x0a28, 0x0628, 0x0e28, //  16
+	0x0128, 0x0928, 0x0528, 0x0d28, 0x0328, 0x0b28, 0x0728, 0x0f28, //  24
+	0x00a8, 0x08a8, 0x04a8, 0x0ca8, 0x02a8, 0x0aa8, 0x06a8, 0x0ea8, //  32
+	0x01a8, 0x09a8, 0x05a8, 0x0da8, 0x03a8, 0x0ba8, 0x07a8, 0x0fa8, //  40
+	0x0068, 0x0868, 0x0468, 0x0c68, 0x0268, 0x0a68, 0x0668, 0x0e68, //  48
+	0x0168, 0x0968, 0x0568, 0x0d68, 0x0368, 0x0b68, 0x0768, 0x0f68, //  56
+	0x00e8, 0x08e8, 0x04e8, 0x0ce8, 0x02e8, 0x0ae8, 0x06e8, 0x0ee8, //  64
+	0x01e8, 0x09e8, 0x05e8, 0x0de8, 0x03e8, 0x0be8, 0x07e8, 0x0fe8, //  72
+	0x0018, 0x0818, 0x0418, 0x0c18, 0x0218, 0x0a18, 0x0618, 0x0e18, //  80
+	0x0118, 0x0918, 0x0518, 0x0d18, 0x0318, 0x0b18, 0x0718, 0x0f18, //  88
+	0x0098, 0x0898, 0x0498, 0x0c98, 0x0298, 0x0a98, 0x0698, 0x0e98, //  96
+	0x0198, 0x0998, 0x0598, 0x0d98, 0x0398, 0x0b98, 0x0798, 0x0f98, // 104
+	0x0058, 0x0858, 0x0458, 0x0c58, 0x0258, 0x0a58, 0x0658, 0x0e58, // 112
+	0x0158, 0x0958, 0x0558, 0x0d58, 0x0358, 0x0b58, 0x0758, 0x0f58, // 120
+	0x00d8, 0x08d8, 0x04d8, 0x0cd8, 0x02d8, 0x0ad8, 0x06d8, 0x0ed8, // 128
+	0x01d8, 0x09d8, 0x05d8, 0x0dd8, 0x03d8, 0x0bd8, 0x07d8, 0x0fd8, // 136
+	0x0139, 0x1139, 0x0939, 0x1939, 0x0539, 0x1539, 0x0d39, 0x1d39, // 144
+	0x0339, 0x1339, 0x0b39, 0x1b39, 0x0739, 0x1739, 0x0f39, 0x1f39, // 152
+	0x00b9, 0x10b9, 0x08b9, 0x18b9, 0x04b9, 0x14b9, 0x0cb9, 0x1cb9, // 160
+	0x02b9, 0x12b9, 0x0ab9, 0x1ab9, 0x06b9, 0x16b9, 0x0eb9, 0x1eb9, // 168
+	0x01b9, 0x11b9, 0x09b9, 0x19b9, 0x05b9, 0x15b9, 0x0db9, 0x1db9, // 176
+	0x03b9, 0x13b9, 0x0bb9, 0x1bb9, 0x07b9, 0x17b9, 0x0fb9, 0x1fb9, // 184
+	0x0079, 0x1079, 0x0879, 0x1879, 0x0479, 0x1479, 0x0c79, 0x1c79, // 192
+	0x0279, 0x1279, 0x0a79, 0x1a79, 0x0679, 0x1679, 0x0e79, 0x1e79, // 200
+	0x0179, 0x1179, 0x0979, 0x1979, 0x0579, 0x1579, 0x0d79, 0x1d79, // 208
+	0x0379, 0x1379, 0x0b79, 0x1b79, 0x0779, 0x1779, 0x0f79, 0x1f79, // 216
+	0x00f9, 0x10f9, 0x08f9, 0x18f9, 0x04f9, 0x14f9, 0x0cf9, 0x1cf9, // 224
+	0x02f9, 0x12f9, 0x0af9, 0x1af9, 0x06f9, 0x16f9, 0x0ef9, 0x1ef9, // 232
+	0x01f9, 0x11f9, 0x09f9, 0x19f9, 0x05f9, 0x15f9, 0x0df9, 0x1df9, // 240
+	0x03f9, 0x13f9, 0x0bf9, 0x1bf9, 0x07f9, 0x17f9, 0x0ff9, 0x1ff9, // 248
+	0x0007, 0x0407, 0x0207, 0x0607, 0x0107, 0x0507, 0x0307, 0x0707, // 256
+	0x0087, 0x0487, 0x0287, 0x0687, 0x0187, 0x0587, 0x0387, 0x0787, // 264
+	0x0047, 0x0447, 0x0247, 0x0647, 0x0147, 0x0547, 0x0347, 0x0747, // 272
+	0x0038, 0x0838, 0x0438, 0x0c38, 0x0238, 0x0a38, 0x0638, 0x0e38  // 280
+};
+
+/* length from 3 to 258 converted to bit strings for use with fixed huffman
+ * coding. It was built by tools/dump_len.c. The format is the following :
+ *   - bits 0..15  = code
+ *   - bits 16..19 = #bits
+ */
+static const uint32_t len_fh[259] = {
+	0x000000,  0x000000,  0x000000,  0x070040,   /* 0-3 */
+	0x070020,  0x070060,  0x070010,  0x070050,   /* 4-7 */
+	0x070030,  0x070070,  0x070008,  0x080048,   /* 8-11 */
+	0x0800c8,  0x080028,  0x0800a8,  0x080068,   /* 12-15 */
+	0x0800e8,  0x080018,  0x080098,  0x090058,   /* 16-19 */
+	0x0900d8,  0x090158,  0x0901d8,  0x090038,   /* 20-23 */
+	0x0900b8,  0x090138,  0x0901b8,  0x090078,   /* 24-27 */
+	0x0900f8,  0x090178,  0x0901f8,  0x090004,   /* 28-31 */
+	0x090084,  0x090104,  0x090184,  0x0a0044,   /* 32-35 */
+	0x0a00c4,  0x0a0144,  0x0a01c4,  0x0a0244,   /* 36-39 */
+	0x0a02c4,  0x0a0344,  0x0a03c4,  0x0a0024,   /* 40-43 */
+	0x0a00a4,  0x0a0124,  0x0a01a4,  0x0a0224,   /* 44-47 */
+	0x0a02a4,  0x0a0324,  0x0a03a4,  0x0a0064,   /* 48-51 */
+	0x0a00e4,  0x0a0164,  0x0a01e4,  0x0a0264,   /* 52-55 */
+	0x0a02e4,  0x0a0364,  0x0a03e4,  0x0a0014,   /* 56-59 */
+	0x0a0094,  0x0a0114,  0x0a0194,  0x0a0214,   /* 60-63 */
+	0x0a0294,  0x0a0314,  0x0a0394,  0x0b0054,   /* 64-67 */
+	0x0b00d4,  0x0b0154,  0x0b01d4,  0x0b0254,   /* 68-71 */
+	0x0b02d4,  0x0b0354,  0x0b03d4,  0x0b0454,   /* 72-75 */
+	0x0b04d4,  0x0b0554,  0x0b05d4,  0x0b0654,   /* 76-79 */
+	0x0b06d4,  0x0b0754,  0x0b07d4,  0x0b0034,   /* 80-83 */
+	0x0b00b4,  0x0b0134,  0x0b01b4,  0x0b0234,   /* 84-87 */
+	0x0b02b4,  0x0b0334,  0x0b03b4,  0x0b0434,   /* 88-91 */
+	0x0b04b4,  0x0b0534,  0x0b05b4,  0x0b0634,   /* 92-95 */
+	0x0b06b4,  0x0b0734,  0x0b07b4,  0x0b0074,   /* 96-99 */
+	0x0b00f4,  0x0b0174,  0x0b01f4,  0x0b0274,   /* 100-103 */
+	0x0b02f4,  0x0b0374,  0x0b03f4,  0x0b0474,   /* 104-107 */
+	0x0b04f4,  0x0b0574,  0x0b05f4,  0x0b0674,   /* 108-111 */
+	0x0b06f4,  0x0b0774,  0x0b07f4,  0x0c0003,   /* 112-115 */
+	0x0c0103,  0x0c0203,  0x0c0303,  0x0c0403,   /* 116-119 */
+	0x0c0503,  0x0c0603,  0x0c0703,  0x0c0803,   /* 120-123 */
+	0x0c0903,  0x0c0a03,  0x0c0b03,  0x0c0c03,   /* 124-127 */
+	0x0c0d03,  0x0c0e03,  0x0c0f03,  0x0d0083,   /* 128-131 */
+	0x0d0183,  0x0d0283,  0x0d0383,  0x0d0483,   /* 132-135 */
+	0x0d0583,  0x0d0683,  0x0d0783,  0x0d0883,   /* 136-139 */
+	0x0d0983,  0x0d0a83,  0x0d0b83,  0x0d0c83,   /* 140-143 */
+	0x0d0d83,  0x0d0e83,  0x0d0f83,  0x0d1083,   /* 144-147 */
+	0x0d1183,  0x0d1283,  0x0d1383,  0x0d1483,   /* 148-151 */
+	0x0d1583,  0x0d1683,  0x0d1783,  0x0d1883,   /* 152-155 */
+	0x0d1983,  0x0d1a83,  0x0d1b83,  0x0d1c83,   /* 156-159 */
+	0x0d1d83,  0x0d1e83,  0x0d1f83,  0x0d0043,   /* 160-163 */
+	0x0d0143,  0x0d0243,  0x0d0343,  0x0d0443,   /* 164-167 */
+	0x0d0543,  0x0d0643,  0x0d0743,  0x0d0843,   /* 168-171 */
+	0x0d0943,  0x0d0a43,  0x0d0b43,  0x0d0c43,   /* 172-175 */
+	0x0d0d43,  0x0d0e43,  0x0d0f43,  0x0d1043,   /* 176-179 */
+	0x0d1143,  0x0d1243,  0x0d1343,  0x0d1443,   /* 180-183 */
+	0x0d1543,  0x0d1643,  0x0d1743,  0x0d1843,   /* 184-187 */
+	0x0d1943,  0x0d1a43,  0x0d1b43,  0x0d1c43,   /* 188-191 */
+	0x0d1d43,  0x0d1e43,  0x0d1f43,  0x0d00c3,   /* 192-195 */
+	0x0d01c3,  0x0d02c3,  0x0d03c3,  0x0d04c3,   /* 196-199 */
+	0x0d05c3,  0x0d06c3,  0x0d07c3,  0x0d08c3,   /* 200-203 */
+	0x0d09c3,  0x0d0ac3,  0x0d0bc3,  0x0d0cc3,   /* 204-207 */
+	0x0d0dc3,  0x0d0ec3,  0x0d0fc3,  0x0d10c3,   /* 208-211 */
+	0x0d11c3,  0x0d12c3,  0x0d13c3,  0x0d14c3,   /* 212-215 */
+	0x0d15c3,  0x0d16c3,  0x0d17c3,  0x0d18c3,   /* 216-219 */
+	0x0d19c3,  0x0d1ac3,  0x0d1bc3,  0x0d1cc3,   /* 220-223 */
+	0x0d1dc3,  0x0d1ec3,  0x0d1fc3,  0x0d0023,   /* 224-227 */
+	0x0d0123,  0x0d0223,  0x0d0323,  0x0d0423,   /* 228-231 */
+	0x0d0523,  0x0d0623,  0x0d0723,  0x0d0823,   /* 232-235 */
+	0x0d0923,  0x0d0a23,  0x0d0b23,  0x0d0c23,   /* 236-239 */
+	0x0d0d23,  0x0d0e23,  0x0d0f23,  0x0d1023,   /* 240-243 */
+	0x0d1123,  0x0d1223,  0x0d1323,  0x0d1423,   /* 244-247 */
+	0x0d1523,  0x0d1623,  0x0d1723,  0x0d1823,   /* 248-251 */
+	0x0d1923,  0x0d1a23,  0x0d1b23,  0x0d1c23,   /* 252-255 */
+	0x0d1d23,  0x0d1e23,  0x0800a3               /* 256-258 */
+};
+
+static uint32_t crc32_fast[4][256];
+static uint32_t fh_dist_table[32768];
+
+/* Make the table for a fast CRC.
+ * Not thread-safe, must be called exactly once.
+ */
+static inline void __slz_make_crc_table(void)
+{
+	uint32_t c;
+	int n, k;
+
+	for (n = 0; n < 256; n++) {
+		c = (uint32_t) n ^ 255;
+		for (k = 0; k < 8; k++) {
+			if (c & 1) {
+				c = 0xedb88320 ^ (c >> 1);
+			} else {
+				c = c >> 1;
+			}
+		}
+		crc32_fast[0][n] = c ^ 0xff000000;
+	}
+
+	/* Note: here we *do not* have to invert the bits corresponding to the
+	 * byte position, because [0] already has the 8 highest bits inverted,
+	 * and these bits are shifted by 8 at the end of the operation, which
+	 * results in having the next 8 bits shifted in turn. That's why we
+	 * have the xor in the index used just after a computation.
+	 */
+	for (n = 0; n < 256; n++) {
+		crc32_fast[1][n] = 0xff000000 ^ crc32_fast[0][(0xff000000 ^ crc32_fast[0][n] ^ 0xff) & 0xff] ^ (crc32_fast[0][n] >> 8);
+		crc32_fast[2][n] = 0xff000000 ^ crc32_fast[0][(0x00ff0000 ^ crc32_fast[1][n] ^ 0xff) & 0xff] ^ (crc32_fast[1][n] >> 8);
+		crc32_fast[3][n] = 0xff000000 ^ crc32_fast[0][(0x0000ff00 ^ crc32_fast[2][n] ^ 0xff) & 0xff] ^ (crc32_fast[2][n] >> 8);
+	}
+}
+
+/* Returns code for lengths 1 to 32768. The bit size for the next value can be
+ * found this way :
+ *
+ *	bits = code >> 1;
+ *	if (bits)
+ *		bits--;
+ *
+ */
+static inline uint32_t dist_to_code(uint32_t l)
+{
+	uint32_t code;
+
+	code = 0;
+	switch (l) {
+	case 24577 ... 32768: code++; /* fall through */
+	case 16385 ... 24576: code++; /* fall through */
+	case 12289 ... 16384: code++; /* fall through */
+	case  8193 ... 12288: code++; /* fall through */
+	case  6145 ...  8192: code++; /* fall through */
+	case  4097 ...  6144: code++; /* fall through */
+	case  3073 ...  4096: code++; /* fall through */
+	case  2049 ...  3072: code++; /* fall through */
+	case  1537 ...  2048: code++; /* fall through */
+	case  1025 ...  1536: code++; /* fall through */
+	case   769 ...  1024: code++; /* fall through */
+	case   513 ...   768: code++; /* fall through */
+	case   385 ...   512: code++; /* fall through */
+	case   257 ...   384: code++; /* fall through */
+	case   193 ...   256: code++; /* fall through */
+	case   129 ...   192: code++; /* fall through */
+	case    97 ...   128: code++; /* fall through */
+	case    65 ...    96: code++; /* fall through */
+	case    49 ...    64: code++; /* fall through */
+	case    33 ...    48: code++; /* fall through */
+	case    25 ...    32: code++; /* fall through */
+	case    17 ...    24: code++; /* fall through */
+	case    13 ...    16: code++; /* fall through */
+	case     9 ...    12: code++; /* fall through */
+	case     7 ...     8: code++; /* fall through */
+	case     5 ...     6: code++; /* fall through */
+	case     4          : code++; /* fall through */
+	case     3          : code++; /* fall through */
+	case     2          : code++; /* fall through */
+	}
+
+	return code;
+}
+
+/* not thread-safe, must be called exactly once */
+static inline void __slz_prepare_dist_table()
+{
+	uint32_t dist;
+	uint32_t code;
+	uint32_t bits;
+
+	for (dist = 0; dist < sizeof(fh_dist_table) / sizeof(*fh_dist_table); dist++) {
+		code = dist_to_code(dist + 1);
+		bits = code >> 1;
+		if (bits)
+			bits--;
+
+		/* Distance codes are stored on 5 bits reversed. The RFC
+		 * doesn't state that they are reversed, but it's the only
+		 * way it works.
+		 */
+		code = ((code & 0x01) << 4) | ((code & 0x02) << 2) |
+		       (code & 0x04) |
+		       ((code & 0x08) >> 2) | ((code & 0x10) >> 4);
+
+		code += (dist & ((1 << bits) - 1)) << 5;
+		fh_dist_table[dist] = (code << 5) + bits + 5;
+	}
+}