[Exim] Wishlist # 189 redux

I wouldn't mind being able to logwrite to syslog or mainlog from the
system_filter. Then I could bitbucket some of the SoBig attachments
without losing logging or having to set up an additional logfile with
matching rotation scripts. Actually it would also work for me if
exicyclog could easily be configured to rotate additional logfiles.
Thanks,
John Dalbec