[Mesa-dev] Fixed function fragment shader to GLSL

[Eric Anholt]

Here's this patch series again, part of the kill-Mesa-IR goal we have
for next release.  It's been no regressions for me for a while, I was
just trying to track down a 2% performance regression on gen6.  It
turns out that on my gen4 system, it's no performance regression, and
on gen7 (at least according to testing with the followon patches to
use the new coegen), it's a ~4% performance win.

While many things were learned in the process, the cause of the 2%
loss appears to come down to some GPU instruction pipelining issue
with lots of handwaving on my part.  When using the new backend, we
generate like 1/3 fewer instructions (after accounting for the 8/16
compile).

I'm not including the patches for using the new backend quite yet, as
there's a functional regression on gm45 in the new backend that I need
to track down first.