[Patch] Improved mouse acceleration

[Simon Thum]

Hello all!

I've managed to spend some time on my improved mouse acceleration again:

 * accel params can be changed at runtime via XChangeDeviceControl
 * above includes the acceleration scheme
 * code structure is OK (at least to me)
 * hotplug should work (untested)

As always, feedback is welcome!

I would like to have some feedback especially on the X*DeviceControl
interface. My message-like approach is a little against the spirit I
think. Also, only a small subset of the parameters declared in Xi.h is
supported by the code, this still needs some work. Getting parameters is
not implemented in libXi/xinput, but already in the server.

If no X*DeviceControl rework is needed, I consider the server side
pretty much done.

Regards,

Simon