MFC r273285:

- Honer MK_KERBEROS for Heimdal rc.d scripts.
- Add rc.c/kerberos to OLD_FILES.
MFC r272562,r272678,r272679

1) Fix the case we have less arguments for format string than we expected.
2) Return error on unsupported format specs.
(both according to POSIX)
3) For %Z format, understand "UTC" name too.

PR:     93197
Merge remote-tracking branch 'freebsd/stable/10' into hardened/10/aslr