Memory issue with libcairo/gl and -nvidia binary driver

[Bryce Harrington]

In testing, we found an oddball issue that with enabling GL for
libcairo, when running under NVIDIA's proprietary driver applications
see significantly increased memory utilization.

  https://bugs.launchpad.net/ubuntu/+source/cairo/+bug/725434

For ubuntu we're working around this by having gl and non-gl binary
packages in libcairo, so wayland can use the former and everything else
the latter.  We will be seeking a more proper fix longer term.

I don't think this affects wayland directly, so just take as an FYI.

Bryce