XvMC client libraries for i810 and via drivers

[Dave Airlie]

I've just committed the i810 and via driver client library automakery to the

xf86-driver-i810 and xf86-driver-via.

I've neither of these to test on so I can't say if the libraries
actually work (I suspect they may need to link with something else)
but they pass distcheck and it is a good start for someone who
actually has the hardware to check them on.

I might be able to dig up an i815 to give it a test on.

Hopefully I haven't broken any builds on other platforms..

Dave.