Start breaking the #include dependencies between pipe drivers and mesa.

Start breaking the #include dependencies between pipe drivers and mesa.

Pipe drivers shouldn't really know much about mesa and certainly shouldn't
be #including files from src/mesa/main and the like.

I've also (in i915simple especially) moved over from GL types to
more conventional int/unsigned usage.  This probably isn't really the
ultimate desired set of types to use - possibly C99 would be better.  It
may even be that a subset of the GL types is preferable.