deraadt and millert ok

long-standing annoyance that atrun's granularity is 10 minutes.
Most at jobs run with a 1 minute granularity.  Jobs submitted via
"at now" or "batch" will run immediately.  Includes a rewritten
cron(8) man page.  at(1) will be integrated more closely into
cron at a future date.
Upgrading notes:
the atrun job in root's crontab should be removed.
the /var/at/spool directory is no longer used

ok henning@, deraadt@

access to devices I/O ports from userland. Only BWX machines supported
for now. Added a man page.
Ok deraadt@, miod@.

ok millert@

aliases to fake up strtou?q().  espie@ OK.

starts, do a chroot to /var/empty and change to user nobody.
hi mom, i'm in jail!

that the first char in the line is not NUL after killing comments.

ok frantzen@

field separators as empty field.  This is not what we want for
whitespace-delimited fields.

o make first arg const since we don't modify it
o use strsep() instead of strtok() as strtok() changes internal state
o add some bounds checking and use strlcat() instead of pointer arithmetic
o ANSI function headers
Originally based on a patch from Lars J. Buitinck but much modified.

generic as /dev/smartcard or similar.
deraadt@ ok.

add more simple filter rule examples
"commit it" deraadt@

some brave soul should look at it.

ok deraadt@