[Bug libstdc++/88322] Implement C++20 library features.

[emsr at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=88322
Bug 88322 depends on bug 88996, which changed state.

Bug 88996 Summary: Implement P0439R0 - Make std::memory_order a scoped enumeration.
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=88996

           What    |Removed                     |Added
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             Status|NEW                         |RESOLVED
         Resolution|---                         |FIXED