[Bug libstdc++/80761] std::set<T,C,A>::insert_return_type uses wrong iterator type

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80761

--- Comment #1 from Jonathan Wakely <redi at gcc dot gnu.org> ---
(and the order of the structure members is also wrong)