[clang] [llvm] [OpenMP] OpenMP 5.1 "assume" directive parsing support (PR #92731)

[Shilei Tian via cfe-commits]

shiltian wrote:

> > don't you need more code in AST?
> 
> Sorry, I don't quite understand the question! Could you elaborate a little please?

I was thinking maybe you need changes in AST related files, like `ASTWriter.cpp`, but that might be not needed as this is adding a new directive.

https://github.com/llvm/llvm-project/pull/92731