[Bug libstdc++/61023] set/map move assignment doesn't move (or copy) the comparator

[redi at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=61023

--- Comment #3 from Jonathan Wakely <redi at gcc dot gnu.org> ---
The standard forgot to say what should happen:
http://cplusplus.github.io/LWG/lwg-active.html#2227