[libclc] [libclc] Add (fast) normalize to CLC; add half overloads (PR #139759)

[Matt Arsenault via cfe-commits]

arsenm wrote:

> The OpenCL-CTS doesn't actually test the geometrics builtins with that option - that's just for bruteforce.

Sounds like a bug

> It passes on an OpenCL implementation which advertises support for single-precision denormals, yes.

Ideally would check it works with denormal flushing forced on, that's the main risk I can see. If I were to stare at this long enough I could probably guess at where the constant was derived from 



https://github.com/llvm/llvm-project/pull/139759