evdev: implement wheel events
evdev: implement wheel events

Mouse wheel events come as EV_REL/REL_WHEEL, and we can convert
them to clutter events on the assumption that scrolling with
the wheel is always vertical.

https://bugzilla.gnome.org/show_bug.cgi?id=705710

ebassi/clutter,ebassi/clutter,djdeath/clutter,jigpu/clutter,Distrotech/clutter,jigpu/clutter,djdeath/clutter,GNOME/clutter,GNOME/clutter,ebassi/clutter,djdeath/clutter,Distrotech/clutter,Distrotech/clutter,GNOME/clutter,ebassi/clutter,jigpu/clutter,GNOME/clutter,jigpu/clutter,djdeath/clutter,jigpu/clutter,Distrotech/clutter,Distrotech/clutter,Distrotech/clutter,djdeath/clutter,jigpu/clutter,GNOME/clutter,djdeath/clutter,ebassi/clutter