-FIXME: Disallow setting $LOGNAME and $USER in crontabs.

-Put info file into appropriate place in spec.

-Add support for binary (pre-parsed) crontabs.

-Send email if cron job parsing fails.
 -Allow for some special address for system crontabs.

crontab.c:crontab_load:
-merge jobs together, not just drop them

timespec-next.c:timespec_next:
-Fix documentation on scheduling limits (10 year limit)

bcron-exec:
-Drop the use of command IDs
-Don't report on execution success
-(minor)Figure out how to open the temporary file with O_APPEND

bcron-start:

bcron-sched:
-If time has jumped backwards or forwards by too large an interval (1
hour?), recalculate all times.
-Fix spurious double-reloading of cronjobs updated by bcron-update.

bcron-update:
-Update just before the top of the minute, instead of just every minute?

bcron-spool:
-Implement support for $BCRON_MAXSIZE and $BCRON_MAXJOBS

bcrontab:
-Make the temporary directory configurable via $TMPDIR or something.

tests:
-Write more tests!
