This request adds the new package mailprocessing.

mailprocessing obsoletes the existing maildirproc package. A little bit of
history on that: I took over upstream development for maildirproc from Joel
Rosdahl last year and added the imapproc utility for performing the same kind
of filtering on IMAP mailboxes. As part of that I renamed the umbrella project
which contains both maildirproc and imapproc to mailprocessing.

I'd like to get this package into Factory eventually and I'd be happy to
maintain it of course.