message: add http 504
diff: @@ -1319,6 +1319,8 @@ static char *http_status_message(int code)
  return "502 Bad Gateway";
  case 503:
  return "503 Service Unavailable";
  + case 504:
  + return "504 Gateway Timeout";
  case 505:
  return "505 HTTP Version Not Supported";
  case 506:
  