MINOR: http-ana: Use a dedicated function to send a response from an http reply

The http_reply_message() function may be used to send an http reply to a
client. This function is responsile to convert the reply in HTX, to push it in
the response buffer and to forward it to the client. It is also responsible to
terminate the transaction.

This function is used during evaluation of http return rules.
diff --git a/include/proto/http_ana.h b/include/proto/http_ana.h
index 62fd74d..f021cb0 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, const struct buffer *msg);
 void http_return_srv_error(struct stream *s, struct stream_interface *si);
 struct buffer *http_error_message(struct stream *s);
+int http_reply_message(struct stream *s, struct http_reply *reply);
 int http_forward_proxy_resp(struct stream *s, int final);
 
 struct http_txn *http_alloc_txn(struct stream *s);