cron(8) now supports random ranges with steps

Thanks to the following
commit
by Todd Miller (millert@),
cron(8)
now supports random values in a range
with a step value
(i.e.
“<lo>~<hi>/<step>”
in
crontab(5) entries):

CVSROOT:	/cvs
Module name:	src
Changes by:	millert@cvs.openbsd.org	2023/05/06 17:06:27

Modified files:
	usr.sbin/cron  : crontab.5 entry.c macros.h 

Log message:
Support random offsets when using ranges with a step value in cron.
This extends the random range syntax to support step values.  Instead
of choosing a random number between the high and low values, the
field is treated as a range with a random offset less than the step
value.  This can be used to avoid thundering herd problems where
multiple machines contact a server all at the same time via cron jobs.

The syntax is similar to the existing range/step syntax but uses a
random range.  For example, instead of "0-59/10" in the minutes
field, "0~59/10" can be used to run a command every 10 minutes where
the first command starts at a random offset in the range [0,9].
The high and low numbers are optional, "~/10" can be used instead.

Requested by job@, OK phessler@