slider: Use key-press instead of key-release
slider: Use key-press instead of key-release

Use key-press instead of key-release and only swallow the event if we
actually respond to the key event. This means we don't need to
special-case left/right in the move_focus function.

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