In
http://mail.python.org/pipermail/email-sig/2004-October/000158.html
I spec'd out a protocol for storing the contents of
large email messages external to the object.  The
thread continues that this isn't completely adequate,
since we'll need a read interface as well, but that
gets problematic.  Follow the thread for details.

This patch implements storage_open(), storage_write()
and storage_close() -- it's a start, and hopefully
someone else can pick it up from here (although not in
time for Python 2.4).