i965: Ask the VBO module to actually use VBOs.

i965: Ask the VBO module to actually use VBOs.

Note that this covers the Begin/End rendering path, but not user vertex
arrays (so we can't drop copy_array_to_vbo_array() code).  Improves
performance of isosurf GLVERTEX|TRIANGLES by 16.7506% +/- 4.98934%
(n=20). No difference on openarena (n=10), which was why this was reverted
back in cbde2765804a4fc62bcf092230a01376aedbf2cd.

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