Changed naming of glsl/default.glsl and hlsl/default.hlsl to glsl/combined_crc*.glsl...

Changed naming of glsl/default.glsl and hlsl/default.hlsl to glsl/combined_crc*.glsl and hlsl/combined_crc*.hlsl - these are now effectively versioned by the crc of the builtin shader code, so if customization is applied it must match the current crc of the engine shader.

This should prevent any future shader version compatibility issues (at the cost of customization being harder to maintain).

Refactored shadermodeinfo related code to clean it up and make it more maintainable.

git-svn-id: svn://svn.icculus.org/twilight/trunk/darkplaces@12283 d7cf8633-e32d-0410-b094-e92efae38249