MINOR: http-ana: Add a txn flag to support soft/strict message rewrites

the HTTP_MSGF_SOFT_RW flag must now be set on the HTTP transaction to ignore
rewrite errors on a message, from HTTP rules. The mode is called the soft
rewrites. If thes flag is not set, strict rewrites are performed. In this mode,
if a rewrite error occurred, an internal error is reported.

For now, HTTP_MSGF_SOFT_RW is always set and there is no way to switch a
transaction in strict mode.
diff --git a/include/types/http_ana.h b/include/types/http_ana.h
index dd55eb8..a352a99 100644
--- a/include/types/http_ana.h
+++ b/include/types/http_ana.h
@@ -87,7 +87,7 @@
 #define HTTP_MSGF_XFER_LEN    0x00000004  /* message xfer size can be determined */
 #define HTTP_MSGF_VER_11      0x00000008  /* the message is HTTP/1.1 or above */
 
-/* unused: 0x00000010 */
+#define HTTP_MSGF_SOFT_RW     0x00000010  /* soft header rewrites, no error triggered */
 
 #define HTTP_MSGF_COMPRESSING 0x00000020  /* data compression is in progress */