evdev: Improve touchpad support and add motion filters

evdev: Improve touchpad support and add motion filters

Touchpad related code has been rewritten and moved to its own file
accessed by evdev via the dispatch interface.

The various functionality implemented are anti-jitter (don't jumping
around), smoother motions, touch detection, pointer acceleration and
some more.

Pointer acceleration is implemented as one generic part, and one touch
specific part (a profile).

Some ideas and magic numbers comes from xserver and
xf86-input-synaptics.

Signed-off-by: Jonas Ådahl <jadahl@gmail.com>