[Bug libstdc++/120548] std::format confuses a negative sign for a thousands digit when formatting floating point numbers

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=120548

--- Comment #2 from Jonathan Wakely <redi at gcc dot gnu.org> ---
It's also wrong for:

format(std::locale("en_GB.UTF-8"), "{:+L}", 123.45) == "+,123.45"
format(std::locale("en_GB.UTF-8"), "{: L}", 123.45) == " ,123.45"