Fix PR libstdc++/78264

[Ville Voutilainen]

On 8 December 2016 at 17:53, Eric Botcazou <ebotcazou@adacore.com> wrote:
> As documented a few lines below in the same file (but I presume that the
> BADNAMES file is long gone), using _N wreaks havoc on Solaris:


I think this documentation has the same content as BADNAMES used to have?
https://gcc.gnu.org/onlinedocs/libstdc++/manual/source_code_style.html