Disable XInput touch device when pen or eraser device reports proximity,
to avoid palm events when writing on a tablet PC with pen + touch.

XNoHands is designed for Tablet PCs running Linux and equipped
with both touch and pen devices. The devices must be logically separate,
and the pen device must report proximity events. (This is the case e.g.
with Wacom-based tablet PCs). XNoHands runs in the background of a user
session and disables the touchscreen device whenever the pen device is in
proximity of the screen. This allows the user to rest their hand on the
screen while writing without causing havoc.