libinput: deprecate WL_CALIBRATION

libinput: deprecate WL_CALIBRATION

The udev property WL_CALIBRATION is an old way of giving Weston a
touchscreen calibration matrix. It is Weston-specific.

The recommended way of setting up a calibration is to use the udev
property LIBINPUT_CALIBRATION_MATRIX, which libinput will load
automatically and therefore applies to all libinput using display
servers and applications.

The syntax of WL_CALIBRATION and LIBINPUT_CALIBRATION_MATRIX is
different as well: WL_CALIBRATION uses pixels as the translation part
units, which makes the values depend on the output resolution.
LIBINPUT_CALIBRATION_MATRIX on the other hand uses normalized units.

Signed-off-by: Pekka Paalanen <pekka.paalanen@collabora.co.uk>
Reviewed-by: Peter Hutterer <peter.hutterer@who-t.net>