The wheel events will end up in GWidget::mousewheel_event(GMouseEvent&)
on the client-side. This patch also implements basic wheel scrolling in
GScrollableWidget via this mechanism. :^)
This was pretty straightforward thanks to the work I did separating out
LibCore from LibGUI already. :^)
- WSMessageLoop now inherits from CEventLoop.
- WSMessage now inherits from CEvent.
- WSMessageReceiver goes away.
Now there is only one event loop in Serenity. Very nice!
