[Bug libstdc++/59675] -D_GLIBCXX_DEBUG asserts to stdout (it should stderr)

[redi at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59675

--- Comment #4 from Jonathan Wakely <redi at gcc dot gnu.org> ---
Yes, we've tried hard to stop polluting our headers with unnecessary includes,
so that would be a step backwards.