Add: absolute touch screen handling in evdevmouse

Some touch screen drivers present themselves as mice with absolute
coordinates. Setting QT_QPA_EVDEV_MOUSE_PARAMETERS=abs will force
qevdevmousehandler to use absolute coordinates, mapped to the screen
from the hardware maximums. These maximum values are read from the
driver using ioctls.
This feature can be safely used with mice, as the features checks will
fail and qevdevmouse will revert back to using relative coordinates.
This way touch screens and mice can work together.

Change-Id: Ic27bda02aa2199f008bac26db75c1f896696f9f5
Reviewed-by: Laszlo Agocs <laszlo.agocs@digia.com>