[Bug c++/98940] Implement C++23 language features

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98940
Bug 98940 depends on bug 106656, which changed state.

Bug 106656 Summary: [C++23] P2513 - char8_t Compatibility and Portability Fixes
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106656

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