[Dovecot] API changes and plugins

[Timo Sirainen]

There's been quite a lot of changes in CVS lately, mostly related to API
changes but also some index file changes. They've both had very little
testing, so there's probably a few bugs left. Especially mbox users
should be careful. pop3 might also be deleting wrong messages..

Anyway. The new mail storage API should allow plugins to hook into
pretty much any operation they want to. It's not exactly pretty with C
syntax, but I think conceptually it's nice object oriented design :)

There's example (non-working) quota plugin at:

http://dovecot.procontrol.fi/patches/quota.c

I also built 0.99.11-test3 from current CVS:

http://dovecot.procontrol.fi/test/