[Bug libstdc++/80493] std::experimental::optional::swap is ill formed

[a...@cloudius-systems.com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80493

--- Comment #3 from Avi Kivity <a...@cloudius-systems.com> ---
Please consider a backport to older branches (5, 6, 7).