[Mesa-dev] V2 GLSL IR & TGSI on-disk shader cache

[Timothy Arceri]

Changes in V2:

- no longer mess around storing/restoring any pointers
- implemented support for compute shaders
- dropped some patches only needed by i965 for now
- add fallback support for shader source that is changed after its compiledi (piglit test on the list)
- simplify cache enable for r600/radeonsi by unconditionally creating the cache in screen_create.
- make glsl version (the version reported as supported by the implemenation at
  compile time) part of the sha1 input rather than adding mesa string to the cache object itself.
  This avoids fallbacks and should be more reliable.
- add any drirc options as sha1 inputs
- some other tidy ups suggested by Nicolai and Marek

In future we probably want to check what other env vars have been set,
but for now the gl/glsl version and drirc options should cover most things.