[Dovecot] Deliver bounces messages if can't write to logs

[Francisco Reyes]

Timo Sirainen writes:

> So there are two solutions for this:
> 1) Change all Dovecot's exit codes to use the standard exit codes.

What advantage, if any, is there to the current return codes that postfix 
doesn't udnerstand?
  
> Both of these are pretty large changes, so they won't happen before
> v1.0..

I used a third solution... changed to use syslog.
I would have preferred to use the logs since it breaks down into informative 
and error outputs, but bouncing mail is not good.. just because it could not 
connect to logs.