macosx: do not abuse "autoscale" to implement a fit to screen feature

(cherry picked from commit 3646cf43)
Signed-off-by: David Fuhrmann <david.fuhrmann@googlemail.com>

modules/gui/macosx/MainMenu.m

@@ -632,7 +632,7 @@ static VLCMainMenu *_o_sharedInstance = nil;
                 var_SetFloat( p_vout, "zoom", 2.0 );
             else
             {
-                var_ToggleBool( p_vout, "autoscale" );
+                [[[[[VLCMain sharedInstance] mainWindow] videoView] window] performZoom:sender];
             }
             vlc_object_release( p_vout );
         }