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

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98940
Bug 98940 depends on bug 106655, which changed state.

Bug 106655 Summary: [C++23] P2295 - Support for UTF-8 as a portable source file encoding
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106655

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