add the same infrastructure to daily; silencing daily needs another step
discussed with ajacoutot@ okan@ todd@ sthen@ deraadt@ jmc@
"immediately commit" deraadt@ (without seeing the final diff)

in preparation for improvements in /etc/daily and /etc/weekly
using feedback and suggestions from jmc@ and sthen@
ok jmc@, and sthen@ agreed with the general direction

noticed by jmc@

for spamd-setup.  OK beck@

Unfortunately this does not fix existing file permissions.
Spotted by Antti Harri <iku at openbsd dot fi>.
OK millert@.

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

are *required*.