[clang] Implement the `fmod` intrinsic (PR #130320)

[Deric C. via cfe-commits]

https://github.com/Icohedron requested changes to this pull request.

For the most part, this PR looks good! Just needs some changes to the codegen test to make it more clear that the implementation is correctly being tested.

https://github.com/llvm/llvm-project/pull/130320