The only reason for the inheritance was to add FDs to the select set.
Since CNotifier is available (and now also quite useful), we can make use of it
instead, and remove the inheritance.
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!
