Remove redundant vlayout masks and wasted vlayout bits

[bsalomon, 2012-07-10 14:16:02]

Now that there is no longer a bit per stage to indicate that a stage uses vertex
positions for coords, the vlayout masks for a stage and the mask for a stage's
texture coordinate bits are redundant. Also, we were still accounting for the
removed bits when determining where the non-stage bits begin. Jeff needs to bump
the stage count and we need to make room for bits.

I started trying to further simplify the masks and the functions that use them.
But I aborted because it seemed like a waste of time in light of the fact that
we plan to remove the vertex layout bitfield entirely.

[TomH, 2012-07-10 14:20:09]

LGTM

[bsalomon, 2012-07-10 15:07:33]

Closed with r4506