[llvm] [llvm] Add support for zero-width integers in MathExtras.h (PR #87193)

[Maksim Levental via llvm-commits]

makslevental wrote:

Just chiming in to comment there's a downstream need for support for zero width integers in CIRCT that goes back ~2 years https://github.com/llvm/circt/issues/2660. So :+1: from me.

https://github.com/llvm/llvm-project/pull/87193