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/include/proto/http_ana.h b/include/proto/http_ana.h
index c226b12..8943576 100644
--- a/include/proto/http_ana.h
+++ b/include/proto/http_ana.h
@@ -52,6 +52,7 @@
 void http_reply_and_close(struct stream *s, short status, struct http_reply *msg);
 void http_return_srv_error(struct stream *s, struct stream_interface *si);
 struct http_reply *http_error_message(struct stream *s);
+int http_reply_to_htx(struct stream *s, struct htx *htx, struct http_reply *reply);
 int http_reply_message(struct stream *s, struct http_reply *reply);
 int http_forward_proxy_resp(struct stream *s, int final);