[Bug c++/91086] std namespace symbols can get their visibility degraded

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=91086

--- Comment #2 from Jonathan Wakely <redi at gcc dot gnu.org> ---
Yes, I think G++ used to not to this, and it was changed to the current
behaviour to avoid such problems.