[Bug c++/88323] implement C++20 language features.

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=88323
Bug 88323 depends on bug 91369, which changed state.

Bug 91369 Summary: Implement P0784R7: constexpr new
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=91369

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