[PATCH] Add feature test macros for POSIX.1-2024.

[Collin Funk]

Collin Funk <collin.funk1@gmail.com> writes:

> * include/features.h (_POSIX_C_SOURCE): Document the value of 202405L
> for POSIX.1-2024.  Set it to 202405L when _GNU_SOURCE or _DEFAULT_SOURCE
> is defined.
> (_XOPEN_SOURCE): Document the value of 800 for POSIX-1.2024.  Set it to
> 800 when _GNU_SOURCE is defined.
> (__USE_XOPEN2K24, __USE_XOPEN2K24XSI): New internal macros.  Set them
> when _POSIX_C_SOURCE is 202405L or greater and/or when _XOPEN_SOURCE is
> 800 or greater.
> * manual/creature.texi (Feature Test Macros): Document the new values
> for _POSIX_C_SOURCE and _XOPEN_SOURCE.
>
> Signed-off-by: Collin Funk <collin.funk1@gmail.com>
> ---
>  include/features.h   | 30 +++++++++++++++++++++++-------
>  manual/creature.texi |  6 +++++-
>  2 files changed, 28 insertions(+), 8 deletions(-)

Hi Carlos,

I saw you are reviewer for this on patchwork. Do you think it is better
to delay this until after the next release?

Maybe it is a bit weird to have the new value for _POSIX_C_SOURCE and
then never use it for declarations.

Collin