Patch: Long SMTP response lines

[Patrick Ben Koetter]

The attached patch sets a new length for SMTP response lines and makes the
length configurable at the same time.

It became necessary to develop this patch, to store (and not truncate) SMTP
responses when multiple virus scanners detect malware and all report the
finding and the overall length exceeds the (old) SMTP response length.

In this case only a truncated string would be written to the datebase, which
made it impossible to come up with complete reporting.

***@rick