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

[ncm at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110339
Bug 110339 depends on bug 119740, which changed state.

Bug 119740 Summary: [C++26] Implement P2714R1, Bind front and back to NTTP callables
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=119740

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