MINOR: flags/mux-h2: decode H2C and H2S flags

The new functions h2c_show_flags() and h2s_show_flags() decode the flags
state into a string, and are used by dev/flags:

  $ ./dev/flags/flags h2c 0x0600
  h2c->flags = H2_CF_DEM_IN_PROGRESS | H2_CF_DEM_SHORT_READ

  $ ./dev/flags/flags h2s 0x7003
  h2s->flags = H2_SF_HEADERS_RCVD | H2_SF_OUTGOING_DATA | H2_SF_HEADERS_SENT \
             | H2_SF_ES_SENT | H2_SF_ES_RCVD
diff --git a/dev/flags/flags.c b/dev/flags/flags.c
index d867ba2..c587cab 100644
--- a/dev/flags/flags.c
+++ b/dev/flags/flags.c
@@ -6,6 +6,7 @@
 #include <haproxy/fd-t.h>
 #include <haproxy/http_ana-t.h>
 #include <haproxy/htx-t.h>
+#include <haproxy/mux_h2-t.h>
 #include <haproxy/stconn-t.h>
 #include <haproxy/stream-t.h>
 #include <haproxy/task-t.h>
@@ -24,10 +25,12 @@
 #define SHOW_AS_HTX   0x00000400
 #define SHOW_AS_HMSG  0x00000800
 #define SHOW_AS_FD    0x00001000
+#define SHOW_AS_H2C   0x00002000
+#define SHOW_AS_H2S   0x00004000
 
 // command line names, must be in exact same order as the SHOW_AS_* flags above
 // so that show_as_words[i] matches flag 1U<<i.
-const char *show_as_words[] = { "ana", "chn", "conn", "sc", "stet", "strm", "task", "txn", "sd", "hsl", "htx", "hmsg", "fd", };
+const char *show_as_words[] = { "ana", "chn", "conn", "sc", "stet", "strm", "task", "txn", "sd", "hsl", "htx", "hmsg", "fd", "h2c", "h2s", };
 
 /* will be sufficient for even largest flag names */
 static char buf[4096];
@@ -134,6 +137,8 @@
 		if (show_as & SHOW_AS_HTX)   printf("htx->flags = %s\n",  (htx_show_flags    (buf, bsz, " | ", flags), buf));
 		if (show_as & SHOW_AS_HMSG)  printf("hmsg->flags = %s\n", (hmsg_show_flags   (buf, bsz, " | ", flags), buf));
 		if (show_as & SHOW_AS_FD)    printf("fd->flags = %s\n",   (fd_show_flags     (buf, bsz, " | ", flags), buf));
+		if (show_as & SHOW_AS_H2C)   printf("h2c->flags = %s\n",  (h2c_show_flags    (buf, bsz, " | ", flags), buf));
+		if (show_as & SHOW_AS_H2S)   printf("h2s->flags = %s\n",  (h2s_show_flags    (buf, bsz, " | ", flags), buf));
 	}
 	return 0;
 }