[Bug libstdc++/109162] C++23 improvements to std::format

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109162

--- Comment #26 from Tomasz Kamiński <tkaminsk at gcc dot gnu.org> ---
The latest commit (optimization) is for GCC 16 only.