MINOR: http-ana: Make the function http_reply_to_htx() public

This function may be used from anywhere to convert an HTTP reply to an HTX
message.
diff --git a/src/http_ana.c b/src/http_ana.c
index f5add7d..f7da268 100644
--- a/src/http_ana.c
+++ b/src/http_ana.c
@@ -4658,7 +4658,7 @@
  * errorfile, an raw file or a log-format string is used. On success, it returns
  * 0. If an error occurs -1 is returned.
  */
-static int http_reply_to_htx(struct stream *s, struct htx *htx, struct http_reply *reply)
+int http_reply_to_htx(struct stream *s, struct htx *htx, struct http_reply *reply)
 {
 	struct buffer *errmsg;
 	struct htx_sl *sl;