macosx: make sure that window is not movable in lion fullscreen mode

this is needed especially for black ui style
(cherry picked from commit 2f6670cc)
Signed-off-by: David Fuhrmann <david.fuhrmann@googlemail.com>

modules/gui/macosx/MainWindow.m

@@ -2119,6 +2119,8 @@ static VLCMainWindow *_o_sharedInstance = nil;
 
     if ([[VLCMain sharedInstance] activeVideoPlayback])
         [o_bottombar_view setHidden: YES];
+    
+    [self setMovableByWindowBackground: NO];
 }
 
 - (void)windowWillExitFullScreen:(NSNotification *)notification
@@ -2159,6 +2161,8 @@ static VLCMainWindow *_o_sharedInstance = nil;
 
     if ([[VLCMain sharedInstance] activeVideoPlayback])
         [o_bottombar_view setHidden: NO];
+    
+    [self setMovableByWindowBackground: YES];
 }
 
 #pragma mark -