[clang] Add tests for CWG issues 6, 212, 232, 2823. (PR #165633)

[Richard Smith via cfe-commits]

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@@ -230,6 +230,37 @@ namespace cwg211 { // cwg211: 2.7
   };
 } // namespace cwg211
 
+namespace cwg212 { // cwg212: yes
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zygoloid wrote:

Ah, yeah, I see that we've removed nearly all of them. I suppose it'd make sense to remove "yes" entirely as an option, given we're so close, and also given that there seems to have been more than one interpretation of what it means -- the latter is my fault, I should have called it "always" or something, or at least written down what I was thinking! :)

https://github.com/llvm/llvm-project/pull/165633