Use anchored failregex for filters to avoid possible DoS -- postfix.conf

Manually picked up from the 0.8 branch limiting lines only to the existing failregex
Use anchored failregex for filters to avoid possible DoS -- cyrus-imap
Use anchored failregex for filters to avoid possible DoS -- couriersmtp.conf
Use anchored failregex for filters to avoid possible DoS -- exim.conf
Use anchored failregex for filters to avoid possible DoS -- lighttpd-fastcgi