glamor: Enabling xephyr and Xorg.

[Eric Anholt]

Here's a short series to make the server glamor stuff actually
testable.  I'm now running glamor for my normal desktop, and the
xephyr bits work too.  I pulled out changes that would have required
more from the intel 2d driver: now it's just a matter of not linking
to the external module's libglamor.so, and not trying to do its own
DRI3 support.  I also pulled out the swap events code: While my timing
tracecs on swap events are looking reasonable, there's really weird
stuff going on with x11perf performance both before and after that
change, and I'm holding off until I can understand it.