[waffle] [RFC] Use cmake config files instead of find

[Dylan Baker]

This patch series adds a cmake PackageConfig file and
PackageConfigVersion file, cmake uses these files much like autotools
uses pkgconfig.

I have tested this against a modified version of piglit, I can push that
branch and provide it for anyone who is interested, I just need to clean
up the patches such that they're ready for mainline.

If/when this series lands it should probably be applied against at least
the 1.4 branch, if not also the 1.3 branch. Since it would be ideal if
downstream projects could rely on this even if they don't need 1.4/1.5
features.