[Bug other/108413] copyrights for gcc 2023

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108413

--- Comment #4 from Jonathan Wakely <redi at gcc dot gnu.org> ---
(In reply to Jakub Jelinek from comment #2)
> libstdc++-v3/src/c++17/fast_float/fast_float.h: unrecognised copyright
> holder: The fast_float authors

I think we need to add a special case for this. That is what it says in
https://github.com/fastfloat/fast_float/blob/main/LICENSE-MIT

> libstdc++-v3/include/c_compatibility/stdatomic.h: unrecognised copyright
> holder: The GCC developers

Oops, this one's wrong, I'll fix it.