[Bug libstdc++/91383] C++17 should remove some library feature deprecated in C++14

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=91383

--- Comment #9 from Jonathan Wakely <redi at gcc dot gnu.org> ---
Some of the removed features are missing deprecated attributes, which should be
fixed.