[Bug libstdc++/59665] User code can cause ambiguous references to "std" in libstdc++

[redi at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59665

--- Comment #1 from Jonathan Wakely <redi at gcc dot gnu.org> ---
*sigh* we'd need to say ::std everywhere to support that code