[RFC/PATCH] Quartz (Mac OS X)

Another pull request that continues from #61.

These commits [the three last ones] and support
for Mac OS X's Quartz using Core Graphics. It
implements full multimonitor support and the
possibility to test it using RandR. I have only tested
it on GNU/Linux with X using `--enable-fakequartz`.
And I cannot say whether or not it will compile for
or run on Mac OS X or if some porting is required.