[Mesa-dev] softpipe two sided fixes

[Dave Airlie]

These two patches fix 13 piglit tests in softpipe, GL2 vertex-program-two-side
and glsl-1.10 interpolation tests.

I'm not 100% sure that my fixes are the correct way to fix the problem,
but I'd probably need some direction if someone knows better, I'm not entirely
happy that the fix is in two places, but I'm not really sure where the best
place to pick between front/back is, and it might be nice to avoid the copying
completely.

Dave.