Updated preprocessor to optionally remove defines from source

[mvaligursky]

We use preprocessor to process hash directives in the GLSL shader. The processor would leave lines like this in the code:

#define VALUE
...
// the value could be used in the code
float count = VALUE;
...
#undef VALUE

but as WGSL language does not support defines at all, the preprocessor can optionally strip those.

This is not used currently, but will be used to process WGSL shaders.