i965: new VS: use the VUE map to write out vertex attributes.

i965: new VS: use the VUE map to write out vertex attributes.

Previously, the new VS backend used two functions,
emit_vue_header_gen6() and emit_vue_header_gen4() to emit the fixed
parts of the VUE, and then a pair of carefully-constructed loops to
emit the rest of the VUE, leaving out the parts that were already
emitted as part of the header.

This patch changes the new VS backend to use the VUE map to emit the
entire VUE.

Reviewed-by: Eric Anholt <eric@anholt.net>