Make QGraphicsScene::touchEventhandler ignore unhandled touch events

This was not done in Qt 4 to play well with the QGesture
implementation, and may need to be revisited if/when we
bring back QGesture for Qt 5.

Change-Id: I4f5f6c8a67387039e838d1ef42ecc70c455ed8a3
Reviewed-by: Morten Johan Sørvig <morten.sorvig@digia.com>

src/widgets/graphicsview/qgraphicsscene.cpp

@@ -5821,7 +5821,7 @@ void QGraphicsScenePrivate::touchEventHandler(QTouchEvent *sceneTouchEvent)
     }
 
     if (itemsNeedingEvents.isEmpty()) {
-        sceneTouchEvent->accept();
+        sceneTouchEvent->ignore();
         return;
     }