message: fix compile error on centos 7
diff: @@ -192,8 +192,24 @@ void server_application::on_call(wampcc::wamp_session& session,
  if (procedure=="time") {
  std::time_t t = std::time(nullptr);
  std::ostringstream utc, loc;
  +
  +#if defined __GNUC__ && __GNUC__ < 5
  + // gcc 4.8 doesn't support std::put_time
  + struct tm tmutc;
  + struct tm tmloc;
  + gmtime_r(&t, &tmutc);
  + localtime_r(&t, &tmloc);
  + char buf[64];
  + asctime_r(&tmutc, buf);
  + buf[strlen(buf)-1] = '\0'; // remove newline
  + utc << buf;
  + asctime_r(&tmloc, buf);
  + buf[strlen(buf)-1] = '\0'; // remove newline
  + loc << buf;
  +#else
  utc << std::put_time(std::gmtime(&t), "%c %Z");
  loc << std::put_time(std::localtime(&t), "%c %Z");
  +#endif
  wampcc::json_object reply;
  reply.insert({"UTC", utc.str()});
  