Gnus Agent patches for IMAP disconnected operation

[Simon Josefsson <jas@pdc.kth.se>]

Ok, I finally took the time and fixed the Gnus Agent bug preventing me
from using it so from now on I'll use the Agent and IMAP disconnected
mode to see how it works. The bugfix and everything else you need for
disconnected IMAP operation are available from:

http://www.extundo.com/nnimap/patches/gnus-agent.html

Be prepared to file bug reports if you decide to test it, I'm sure
there are bugs in it.

I'm aware of two limitations.

1) The Agent can't move articles into unplugged mailboxes (and have
   them be synchronized to the server). As I never do such things I
   don't care much but it will be fixed eventually, I posted a patch
   for that here some months ago so it shouldn't be hard.

2) If you use another client (or even another instance of Gnus/nnimap)
   to read mail on your IMAP server when unplugged, Gnus doesn't guess
   the number of unread articles in your mailboxes correctly when you
   reconnect. Entering the mailbox fetches correct information from
   the server and things are back to normal. I'm going to fix this one
   first.