All the rest of XI uses rc and returns rc in case of error, so make
mpx-related stuff comply. This stops the rest of XI sending the error
manually.
This is just a cosmetic change to be in line with the rest.
We free the ValuatorClassRec quite regularly. If a SIGIO is handled while
we're swapping device classes, we can bring the server down when we try to
access lastx/lasty of the master device.
Adding PointerKeyboardPairingChanged event
Correct error values for XWarpDevicePointer
dix: Adding device argument to SendMappingNotify
Adding spriteOwner flag to devices