[Bug c++/110338] Implement C++26 language features

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110338
Bug 110338 depends on bug 114457, which changed state.

Bug 114457 Summary: [C++26] P2795R5 - Erroneous behavior for uninitialized reads
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114457

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