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

[A. Jiang via llvm-commits]

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@@ -24,7 +24,12 @@
 #endif
 
 #ifdef __cplusplus
-#  include <ctgmath>
+#  if _LIBCPP_STD_VER >= 17
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frederick-vs-ja wrote:

Yeah. I'm correspondingly changing `<ctgmath>` and `<ccomplex>` now.

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