The quartett of new config functions is:
	libinput_device_config_accel_get_profiles
	libinput_device_config_accel_get_profile
	libinput_device_config_accel_set_profile
	libinput_device_config_accel_get_default_profile

The profile defines how the pointer acceleration works, from a very high-level
perspective. Two profiles are on offer, "adaptive", the standard one we have
used so far and "flat" which is a simple multiplier of input deltas and
provides 1:1 mapping of device movement vs pointer movement.

The speed setting is on top of the profile, a speed of 0 (default) is the
equivalent to "no pointer acceleration". This is popular among gamers and
users of switchable-dpi mice.

The flat profile unnormalizes the deltas, i.e. you get what the device does
and any device below 800dpi will feel excruciatingly slow. The speed range
[-1, 1] maps into 0-200% of the speed. At 200%, a delta of 1 is translated
into a 2 pixel movement, anything higher makes it rather pointless.

The flat profile is currently available for all pointer devices but touchpads.

https://bugs.freedesktop.org/show_bug.cgi?id=89485



Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>
Reviewed-by: Hans de Goede <hdegoede@redhat.com>