manual: Complete @standards in creature.texi.

[Rical Jasan]

On 06/16/2017 06:10 AM, Zack Weinberg wrote:
> On Fri, Jun 16, 2017 at 8:24 AM, Florian Weimer <fweimer@redhat.com> wrote:
>> On 06/16/2017 01:09 PM, Rical Jasan wrote:
>>>       * creature.texi (_THREAD_SAFE): Annotate as obsolete.
>>>       (_REENTRANT): Likewise.
>>
>> Content-wise, this looks correct to me (the macros are obsolete).
> 
> And as far as I was able to determine when I made them aliases for
> _POSIX_C_SOURCE=199506L, they were never part of any standard we track
> conformance with, either, so I also endorse this change.

Since not being from any particular standard is kind of an odd case,
should we maybe say something like, "These macros are not known to have
ever been part of any standard.", maybe at the end of the description?

In general, I would like to see anything that gets marked as Obsolete
with something in the description that provides a bit of history.

Rical