Fixed avfmediaplayersession.mm for OSX 10.10 Yosemite.

Implicit cast caused build to fail. Explicit cast builds fine.

Task-number: QTBUG-41136
Change-Id: I0147c26a0f8b8198d6ed9944311547b81a50bccb
Reviewed-by: Yoann Lopes <yoann.lopes@digia.com>

src/plugins/avfoundation/mediaplayer/avfmediaplayersession.mm

@@ -295,7 +295,7 @@ static void *AVFMediaPlayerSessionObserverCurrentItemObservationContext = &AVFMe
     //AVPlayerItem "status" property value observer.
     if (context == AVFMediaPlayerSessionObserverStatusObservationContext)
     {
-        AVPlayerStatus status = [[change objectForKey:NSKeyValueChangeNewKey] integerValue];
+        AVPlayerStatus status = (AVPlayerStatus)[[change objectForKey:NSKeyValueChangeNewKey] integerValue];
         switch (status)
         {
             //Indicates that the status of the player is not yet known because