Support absolute pointer devices

Detecting them is a bit of guesswork: if a device is a pointer device and has
a calibration matrix option, then the device must be an abs device.

Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>
Require libinput 0.7.0

We've required this already anyway, now we have the libinput version to match
though

Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>