Continuation of #131332.
Including built-in headers in VS2019 ends up including `corecrt_math.h`
as a side effect, which has many functions that overlap in name with
our stubs.
This puts the conflicting functions inside its own namespace (`glsl`)
and declares macros for them.
(Note this has the side effect of not allowing us to use those as
variable names)
This also removes the `<cassert>` and `<cstdio>` includes.
Pull Request: https://projects.blender.org/blender/blender/pulls/131386
bd1f4ec23c