[Bug libstdc++/108053] std::visit_format_arg should hide __int128 and other extensions behind a handle

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108053

--- Comment #2 from Jonathan Wakely <redi at gcc dot gnu.org> ---
Libc++ fixed an equivalent issue with
https://github.com/llvm/llvm-project/commit/e948cab07d68c240723a12cdc151d09c5cef87ba