[Bug libstdc++/94498] std::basic_string_view::copy not qualified constexpr in c++2a

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94498

Jonathan Wakely <redi at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|ASSIGNED                    |RESOLVED
         Resolution|---                         |FIXED
   Target Milestone|9.4                         |10.0

--- Comment #2 from Jonathan Wakely <redi at gcc dot gnu.org> ---
I was going to backport this to gcc-9 but it requires std::copy to be
constexpr, and I do not plan to backport that.

So fixed for gcc-10.