[Mesa-dev] i965 precompile improvements

[Kenneth Graunke]

Here's a follow-up to my last series.  Now that the FS precompile
doesn't completely keel over in the face of texturing, I figured I'd
try to fix it up.

The result is pretty good: we now guess correctly most of the time.
On Sandybridge, my L4D2 timedemo has only 39 recompiles, as opposed to
206 before the SamplerUnits rework began.  With that in mind, I've
reenabled the precompile, which avoids a lot of stuttering on startup.

Someday I need to go back and see if anything can be done about Gen4-5.
I'm not sure how the precompile will do on those platforms.

This does contain one important fix: patch 8 fixes a regression from my
last series where I totally broke the VS precompile.