[Bug c/81404] suggested hints for standard C macros should avoid GCC predefined macros

[dmalcolm at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81404

--- Comment #5 from David Malcolm <dmalcolm at gcc dot gnu.org> ---
Candidate patch:
  https://gcc.gnu.org/ml/gcc-patches/2017-10/msg01083.html