[Bug libstdc++/88322] Implement C++20 library features.

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=88322
Bug 88322 depends on bug 108053, which changed state.

Bug 108053 Summary: std::visit_format_arg should hide __int128 and other 
extensions behind a handle
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108053

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