backport of 2 commits for Mac on master:
backport of 2 commits for Mac on master:

    0d32bc8358436429fff9251377d86bb03c2aaf1f
        suppress a senseless simulated debug/warning message
        The Mac video widget delegate printed an incomprehensible and
        irrelevant vout log message on stdout. Removed.
    5768c95dd0ee6f12d38efcbe8dcf5d6f3f74a9f1
        work around an over-releasing regression in Qt 5.8.0
        Also: use @autoreleasepool instead of an explicit
        NSAutoreleasePool instance.

KDE/phonon-vlc,KDE/phonon-vlc,KDE/phonon-vlc