Cocoa: Fix menu item activation.

Handle the action message on the application delegate.

Change-Id: I23686fd6e936a4dbbb141da3dd04a64cbf6a051a
Reviewed-by: Bradley T. Hughes <bradley.hughes@nokia.com>

src/plugins/platforms/cocoa/qcocoaapplicationdelegate.mm

@@ -354,7 +354,7 @@ static void cleanupCocoaApplicationDelegate()
 - (void)qtDispatcherToQAction:(id)sender
 {
     Q_UNUSED(sender);
-    //[[NSApp QT_MANGLE_NAMESPACE(qt_qcocoamenuLoader)] qtDispatcherToQAction:sender];
+    [qtMenuLoader qtDispatcherToQAction:sender];
 }
 
 @end