[Dovecot] Log successful login plain text password

[Joseph Tam]

Marco Fretz writes:

> Maybe you can find a way in this direction
>
> http://wiki2.dovecot.org/HowTo/ConvertPasswordSchemes

I've sync'd a separate password system by process tracing dovecot's
auth process and dumping out the arguments of read() calls for some
fixed set of descriptors and piping it into password synching script.
A bit of a hack, but it works without having to touch dovecot.

Joseph Tam <jtam.home at gmail.com>