[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 100974, which changed state.

Bug 100974 Summary: [C++23] Implement if consteval
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100974

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