[sroll-bar] Mouse-wheel support
[sroll-bar] Mouse-wheel support

Turning the mouse-wheel with mouse cursor positioned above a
scroll-bar scrolls up/down/left/right.

pwithnall/mx,clutter-project/mx,pwithnall/mx,jonnylamb/mx,jonnylamb/mx,pwithnall/mx,jonnylamb/mx,clutter-project/mx,clutter-project/mx,jonnylamb/mx,pwithnall/mx,clutter-project/mx