IMPORT: sha1: import SHA1 functions

This is based on the git SHA1 implementation and optimized to do word
accesses rather than byte accesses, and to avoid unnecessary copies into
the context array.
diff --git a/include/import/sha1.h b/include/import/sha1.h
new file mode 100644
index 0000000..33ee530
--- /dev/null
+++ b/include/import/sha1.h
@@ -0,0 +1,35 @@
+/*
+ * Based on the git SHA1 Implementation.
+ *
+ * Copyright (C) 2009-2015, Linus Torvalds and others.
+ *
+ * SHA1 routine optimized to do word accesses rather than byte accesses,
+ * and to avoid unnecessary copies into the context array.
+ *
+ * This was initially based on the Mozilla SHA1 implementation, although
+ * none of the original Mozilla code remains.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation, version 2.1
+ * exclusively.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
+ */
+
+typedef struct {
+	unsigned long long size;
+	unsigned int H[5];
+	unsigned int W[16];
+} blk_SHA_CTX;
+
+void blk_SHA1_Init(blk_SHA_CTX *ctx);
+void blk_SHA1_Update(blk_SHA_CTX *ctx, const void *dataIn, unsigned long len);
+void blk_SHA1_Final(unsigned char hashout[20], blk_SHA_CTX *ctx);