[Bug libstdc++/110339] Implement C++26 library features

[redi at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110339
Bug 110339 depends on bug 110356, which changed state.

Bug 110356 Summary: [C++26] P2637R3 Member visit
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110356

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