Fix a memory leak in QFseventsFileSystemWatcherEngine

Add a missing NSAutoReleasePool

Task-number: QTBUG-38637
Change-Id: Ib69d92b6e9c4327cbb74f7814a45773bfc2ee526
Reviewed-by: Erik Verbruggen <erik.verbruggen@digia.com>

src/corelib/io/qfilesystemwatcher_fsevents.mm

@@ -496,6 +496,7 @@ QStringList QFseventsFileSystemWatcherEngine::removePaths(const QStringList &pat
 bool QFseventsFileSystemWatcherEngine::startStream()
 {
     Q_ASSERT(stream == 0);
+    Q_AUTORELEASE_POOL(pool)
     if (stream) // This shouldn't happen, but let's be nice and handle it.
         stopStream();