Only keycodes from backend server with fully matching
keysyms are mapped to local keycodes and processed as
input events.
A truly independent backend server keymap can be obtained
by using a separate master device.
Use new dmxCoreMotion2() function which enqueues motion events with
GetPointerEvents()/mieqEnqueue().
The clipAxis() code in GetPointerEvents() is causing some grief. The
limits seem to have always been (0,0) according to the original calls
to InitValuatorAxisStruct() in dmxinputinit.c.
Terrible hack for now: Call InitValuatorAxisStruct() with hard-coded max
values of 1280 (my screen width).
