[Mesa-dev] A couple more to make the preprocessor conform better

[Carl Worth]

This continues my ongoing series to make the preprocessor conform more
precisely to the specifications.

I am sprinkling these patches out as I write and test them because they are
each logically independent. If people would prefer that I batch them up and
submit them as a single series, I can do that instead.

I am adding "make check" tests for each of the issues I fix with each patch. I
haven't been running piglit, but I will do a piglit run over the whole series
before I push anything to ensure I haven't caused any regressions.

With the two patches emailed here, there's only one logical change. I did
write it in two pieces though, so I'm submitting it that way. If anyone would
prefer these to be squashed, I could easily do that.

-Carl