[Bug libstdc++/78486] feature request: std::iu16stringstream std::ou16stringstream, and utf8

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78486

--- Comment #4 from Jonathan Wakely <redi at gcc dot gnu.org> ---
That was never in <iostream> in the first place, so it can't have been removed.