acecad: fake device limits == screen limits in xserver 1.4 for xinput

acecad: fake device limits == screen limits in xserver 1.4 for xinput

xserver 1.4 does not do automatic coordinate scaling, so we have to do
it manually. But this breaks xinput clients that do their own scaling
using the device limits as reference. Pretend that they are the same as the
screen limits to work around this.