message: mac: show dialog when checking for updates.
diff: void SparkleHelper::checkForUpdate()
  {
  - [[SUUpdater sharedUpdater] checkForUpdatesInBackground];
  + // [[SUUpdater sharedUpdater] checkForUpdatesInBackground];
  + [[SUUpdater sharedUpdater] checkForUpdates:nil];
  }
  void SparkleHelper::setAutoUpdateEnabled(bool enabled)
  