fix "delay" when using @daily,@weekly in anacrontab

Hi,

Here is a new manpage for anacrontab. I noticed **RANDOM_DELAY** , I implemented it.
It works for crontab too, it is just not yet documented.

There was an other bug: if someone use a anacrontab like this:
```
@weekly 15 jobid echo test
```
the 15 minutes delay was ignored when building the schedule. 
(and accuracy and delay are two different things)

By the way, do you like comments in the code ?