[Bug libstdc++/107761] Implement C++23

[gonzalo.gadeschi at gmail dot com via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107761

--- Comment #2 from gnzlbg <gonzalo.gadeschi at gmail dot com> ---
Update: the reference implementation is now merged into libc++ and will release
with LLVM 17.