[Bug libstdc++/69350] Don't define the C99 functions in -std=c++98 mode

[pinskia at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=69350

--- Comment #2 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
(In reply to Jonathan Wakely from comment #0)
>  (that won't be
> possible for GNU/Linux unless/until we stop defining _GNU_SOURCE implicitly).

Which is PR 11196 .