Fix input_mnager behaviour to what it was intended. Patch idea by Dylan.

modules/gui/qt4/input_manager.cpp

@@ -581,7 +581,7 @@ static int InterfaceChanged( vlc_object_t *p_this, const char *psz_var,
     static int counter = 0;
     InputManager *im = (InputManager*)param;
 
-    counter = counter++ % 4;
+    counter = ++counter % 4;
     if(!counter)
         return VLC_SUCCESS;
     IMEvent *event = new IMEvent( PositionUpdate_Type, 0 );