[libcxx] [llvm] [libc++] Deprecate and remove meaningless `<cxxx>` headers (PR #111615)

[Louis Dionne via llvm-commits]

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@@ -23,4 +23,12 @@
 #  pragma GCC system_header
 #endif
 
+#if _LIBCPP_STD_VER >= 17 && defined(__DEPRECATED) && __DEPRECATED && !defined(_LIBCPP_DISABLE_DEPRECATION_WARNINGS)
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ldionne wrote:

Should we instead set `_LIBCPP_DISABLE_DEPRECATION_WARNINGS` when `-Wno-deprecated` is passed?

https://github.com/llvm/llvm-project/pull/111615