Synaptics acceleration support

[Simon Thum]

Ben Gamari wrote:
> be too difficult to implement. Am I wrong? If not, I could potentially 
> take a stab at it.
Oh, I overlooked that one earlier. In the docs to ptr accel I've
described how to detect whether the server is configured to do
predictable pointer accel. The job would be defeating deriver accel in
that case. However you'd need to do a XSERVER >= 1.6 compile-time check
since else you can't expect prtaccel.h to be present. If your
autoconf-foo is better than mine, you may as well simply check for the
header itself.

So yes, you're welcome.