Merge branch 'merged-scroll-events'

Merge branch 'merged-scroll-events'

This is merged on top of the wheel normalization patches. Those introduced an
axis source and an extra "discrete" value to the various internal and external
APIs. This branch changed from a single value to passing dx/dy into all scroll
events.

The conflicts are to change everything to take x, y, x_discrete, y_discrete as
values (and the source axis mask of course).

Conflicts:
	src/evdev-mt-touchpad-edge-scroll.c
	src/evdev.c
	src/libinput-private.h
	src/libinput.c