Sync with FreeBSD:

Sync with FreeBSD:

- mktime() already does daylight savings.

- Explain the format of the at.allow and at.deny files in detail.

- mdoc improvements.

- Use MAXLOGNAME - 1 instead of UT_NAMESIZE.

- Do not pretend there is something like '/etc/utmp'.

- Add the SUSv3 -l option to at.  This is an alias for atq. Allow job ids
to be specified on the command line for which information should be
reported.

- Document the fact that at(1) is run through cron(8).  This affects the
granularity of the at queue runs.

- Organize #includes.

- Remove the -V [version number] option.

- Implement the POSIX 1003.1-2001 -r and -t options in at(1).

- Warns cleanup and diff reduction from FreeBSD.

- Remove some unsafe function calls from the signal handlers.

- Fix privileges macros.

Obtained-from: FreeBSD