[Bug libstdc++/58952] Construct "std::getchar()" rejected when getchar is macro in C library

[redi at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58952

--- Comment #2 from Jonathan Wakely <redi at gcc dot gnu.org> ---
Oh sorry, I didn't read your report properly - so we're missing the #undef that
would fix it