[Mesa-dev] ARB_enhanced_layout compile-time-constants V3

[Timothy Arceri]

This series adds support for compile time constants and also adds
subroutine index qualifier support which was missing for ARB_explicit_uniform_location.

This series applies on top of a clean-up series[3]

V3: 
- Some refactoring and a bug fix based on Emil's feedback on V2.
- Series overhauled to reduce code churn while still keeping patches
as small as possible for easy review.
- Improvements to handling compute shader local_size layout qualifiers
- Rebased on top of clean-up series [3]

V2: Validation of minimum qualifier value moved to the helper functions, all
qualifiers will now always have the mimimum value checked. Split the patches
that move validation out of the parser and add the compile time constant
support into smaller patches where possible. 

Piglit tests have been reviewed and pushed to master, there is one outstanding
that tests querying of the subroutine index [1].

The extension is disabled by default until the remaining features are added.

MESA_EXTENSION_OVERRIDE=GL_ARB_enhanced_layouts can be used for testing.

You can get the series from my arb_enhanced_layouts6 branch [2]

[1] https://patchwork.freedesktop.org/patch/63795/
[2] https://github.com/tarceri/Mesa_arrays_of_arrays.git
[3] https://patchwork.freedesktop.org/series/728/