[clang] [Clang] restrict use of attribute names reserved by the C++ standard (PR #106036)

[via cfe-commits]

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@@ -177,6 +177,26 @@ static bool isLanguageDefinedBuiltin(const SourceManager &SourceMgr,
   return false;
 }
 
+static bool isReservedAttrName(Preprocessor &PP, IdentifierInfo *II) {
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cor3ntin wrote:

`likely` is reserved, `likely()` is not.
Also, as we support attributes in older language modes as extensions so we should take that into account.
Does C has similar restrictions?

https://github.com/llvm/llvm-project/pull/106036