The maillog package will write to the system logger if it can't write to
the mail log. It does this only once to avoid spamming the system logger
on misconfigurations.
This patch adds a test for this condition.
The default INFO logs are more oriented towards debugging and can be
a bit too verbose when looking for high-level information.
This patch introduces a new "maillog" package, used to log messages of
particular relevance to mail transmission at a higher level.
