- System V names are now obsolescent.
- The main data format now uses %z.
- The code now conforms to RFC 8536 for early timestamps.
- Support POSIX.1-2024, which removes asctime_r and ctime_r.
- Assume POSIX.2-1992 or later for shell scripts.
- SUPPORT_C89 now defaults to 1.
- Include two upstream patches for month names as in April vs Apr.
Harden against links to removed zones.
Resolves: #2310315
