[Bug libstdc++/106749] Implement C++23 library features

[tkaminsk at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106749
Bug 106749 depends on bug 107761, which changed state.

Bug 107761 Summary: Implement C++23 <mdspan>
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107761

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