build: check if libinput supports high-res scroll

Starting with Linux Kernel v5.0 two new axes are available for
mice that support high-resolution wheel scrolling: REL_WHEEL_HI_RES and
REL_HWHEEL_HI_RES.

Both axes send data in fractions of 120 where each multiple of 120
amounts to one logical scroll event. Fractions of 120 indicate a wheel
movement less than one detent.

Three new events are now available on libinput:
LIBINPUT_EVENT_POINTER_SCROLL_WHEEL,
LIBINPUT_EVENT_POINTER_SCROLL_FINGER, and
LIBINPUT_EVENT_POINTER_SCROLL_CONTINUOUS.
These events replace the LIBINPUT_EVENT_POINTER_AXIS event, so new
clients should simply ignore that event.

Also, two new APIs are available to access the high-resolution data:
libinput_event_pointer_get_scroll_value() and
libinput_event_pointer_get_scroll_value_v120().

Add a project argument (LIBINPUT_HAS_SCROLL_VALUE120) to allow
building against old versions of libinput or, where high-resolution
scroll is available, support it.

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