[Mesa-dev] Initial version of threaded GL dispatch V2

[Timothy Arceri]

Since Marek is busy with other things at the moment I thought I'd
try keep the momentum going on getting the initial implementation
committed.

Gregory Hainaut has fixed the piglit crashes in the previous
version, and I've addressed the review feedback. I've also pushed
some standalone patches.

The only thing I didn't address was adding EGL/GBM support as that
code is unfamiliar to me and it looks like we can pass a -plaform=
arg to piglit to get waffle to use a different platform for testing
anyway (also Gregory did some basic EGL testing with PCSX2).

One thing that still concerns me is the use of _mesa_glthread_finish() 
This seems to assume that the context itself is only accessed by a
single thread. See patch 14, 22 & 24 as an example of what I mean. I'm
not sure how this should be solved (assuming its a real problem).

Please review.