[clang] [OpenACC] Add 'clause' parsing infrastructure plus a few clauses (PR #75052)

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@@ -69,6 +69,29 @@ OpenACCDirectiveKindEx getOpenACCDirectiveKind(Token Tok) {
       .Default(OpenACCDirectiveKindEx::Invalid);
 }
 
+// Translate single-token string representations to the OpenCC Clause Kind.
+OpenACCClauseKind getOpenACCClauseKind(Token Tok) {
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cor3ntin wrote:

Should this be static (ditto for the rest of the functions in the files)

https://github.com/llvm/llvm-project/pull/75052