[clang] [llvm] [OpenMP] Add directive spellings introduced in spec v6.0 (PR #141772)

[Krzysztof Parzyszek via llvm-commits]

kparzysz wrote:

Hi @alexey-bataev, could you check if you're ok with this?  I had to modify a few clang tests to accommodate this change.

https://github.com/llvm/llvm-project/pull/141772