[Mesa-dev] SSO fixes V2

[Timothy Arceri]

V2: I've dropped most of my fix from V1 and instead included the fixes
from Gregory which I have cleaned up slightly. I've also added a
patch to remove inactive varyings with an explicit location.

The removal of inactive varyings with an explicit location results
in no changes in the public shader-db although its unlikely many if any 
shaders in there make use of SSO.

I also ran the series on Intels CI system with no regressions.

The series fixes the following piglit tests:
http://patchwork.freedesktop.org/patch/63564/
http://patchwork.freedesktop.org/patch/63565/