i965: Move VUE map computation to once at VS compile time.

i965: Move VUE map computation to once at VS compile time.

With this and the previous patch, 640x480 nexuiz is running 0.169118%
+/- 0.0863696% faster (n=121).  On a VS state change microbenchmark,
performance is increased 8.28645% +/- 0.460478% (n=52).

v2: Fix CACHE_NEW_VS comment.

Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>