libinput-device: use the new merged scroll events
libinput-device: use the new merged scroll events

libinput now provides a single event for scroll events. Extract the axes from
that event and split them into the wl events.

Signed-off-by: Peter Hutterer <b9c50af7afa7642f6f854434cda9ffe54ece8b85@who-t.net>
Reviewed-by: Jonas Ådahl <67dcd8a17e758192e0cbb577ce1d62cc7da6cf49@gmail.com>

udoprog/weston,eyolfson/weston,xorgy/weston,jonnylamb/weston,kwm81/weston,Gnurou/weston,eyolfson/weston,giucam/weston,Gnurou/weston,Fantu/compositor-spice,krezovic/weston,jonnylamb/weston,Fantu/compositor-spice,Tarnyko/weston-xdg_surface_present,kwm81/weston,sir-murray/weston,mchalupa/weston,giucam/weston,udoprog/weston,krezovic/weston,sir-murray/weston,Fantu/compositor-spice,Tarnyko/weston-xdg_surface_present,xorgy/weston,mchalupa/weston