i965: Add scalar GS input lowering code.
i965: Add scalar GS input lowering code.

We really ought to compute the VUE map at link time and stash it, rather
than recomputing it here, but with the mess of program structures I
wasn't sure where to put it.  We can improve that later.

Signed-off-by: Kenneth Graunke <bd2562f754ec92342f93f61c25d731e290a2ffa8@whitecape.org>
Reviewed-by: Kristian Høgsberg <ca9b5b1e27d4fa7f4ba6848bdd08ca52cfd6330c@bitplanet.net>

metora/MesaGLSLCompiler,metora/MesaGLSLCompiler,metora/MesaGLSLCompiler