Major OSL changes to catch up

flat_map optimization for runtime specialization:

https://github.com/imageworks/OpenShadingLanguage/commit/0365a1cbeec6be35bf47a355b65d88a88b56c159

 

unspecified array length for shader parameters:

https://github.com/imageworks/OpenShadingLanguage/commit/5b04e8de69974c0653c2542f337713e2262e54e6

 

fix for composite bsdf weighting:

https://github.com/imageworks/OpenShadingLanguage/commit/e3093d75ee0f92d79140a48d4f3877e7b95a302c

 

optimization to reduce atomic read:

https://github.com/imageworks/OpenShadingLanguage/commit/e70e7dedec00f44b1f2e6806aea54c57a3e696d3