Meson

You all knew it was coming, right? 😆

This is an initial meson based build system for waffle, it wraps cmocka so you don't have to install it or vendor it internally for mac and windows. It vendors wglext.h, but I'm planning to replace that with a wrap soon, just trying to decide the best way to make that wrap.

Anyway, this has been tested on windows, linux, and macos. It builds successfully and has been used for a couple of limited piglit runs.

I'd like to leave the cmake build in place for a while so that we have a fallback when bugs are discovered.