Fixed wacom emulation
- for absolute mode, scale coordinates to the real device maximum values,
since some drivers (on Haiku and Linux at least) need them as such,
and the HID descriptor is boggus on some models anyway,
- keep the coordinates even when no button is pressed, on real tablet
the pen is sensed on the surface even without direct contact,
and drivers expect this,
- map left button to pressure according to what the Haiku driver wants,
- map the right button to the pen button,
- map the middle button to the eraser,
- use asynchronous reporting as the hid code does, stops the Haiku driver
(and probably others) from spending 50% cpu polling for changes.
Signed-off-by: François Revol <revol@free.fr>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>