Added a new flag HLSLCC_FLAG_COMBINE_TEXTURE_SAMPLERS which creates a new GLSL sampler for every unique texture+sampler pair used in HLSL.
The new sampler names are the texture name and sampler name delimited by '_X_'.
For example, the HLSL code "diffuseTexture.Sample(linearSampler, texcoords);" will become a GLSL sampler named "diffuseTexture_X_linearSampler".
The delimiter '_X_' is used so other code can easily split the GLSL sampler name into the original texture and sampler components.
Merge commits for sampler uniform per texture+sampler pair (issue #22)
Ignore combine_texture_samples flag prior to SM4
Fix texelFetch with HLSLCC_FLAG_COMBINE_TEXTURE_SAMPLERS

We need a sampler without any sampler state for texel fetch.
Fixes undeclared samplers in tests\ps4\HDAO.
Fix double underscore in sampler names.

Found with tests\ps4\array_of_textures
error C7528: OpenGL reserves names containing '__'
Remove assert on resource locations with HLSLCC_FLAG_COMBINE_TEXTURE_SAMPLERS

No need to assert, just let the driver auto-assign locations.
Different way to fix double underscore in sampler names.
texture gather plus HLSLCC_FLAG_COMBINE_TEXTURE_SAMPLERS
Merge branch 'nosferalatu-master'