WindowServer+LibGUI: Allow arbitrary number of rects in messages.

To get truly atomic updates, add a mechanism for passing arbitrary amounts
of extra data along with WindowServer messages. This allows us to pass all
the rects in a single message.

Servers/WindowServer/WSMenu.cpp

@@ -134,6 +134,8 @@ void WSMenu::event(CEvent& event)
         clear_hovered_item();
         return;
     }
+
+    CObject::event(event);
 }
 
 void WSMenu::clear_hovered_item()