[Bug libstdc++/37475] [DR 382] codecvt::do_in/do_out functions return "ok" when the output sequence has zero length

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=37475

--- Comment #4 from Jonathan Wakely <redi at gcc dot gnu.org> ---
Oops, I meant 382 is NAD
http://cplusplus.github.io/LWG/lwg-closed.html#382

I'm not sure what (if anything) we need to do here though, someone needs to
re-analyze.