[Dovecot] 1.0-test18

http://dovecot.org/test/

Again mostly just mbox fixes. The good thing is that the code is only getting cleaner and more understandable with every release. But I think it's clean enough now that this release should work :)

It also has checkpassword passdb support. Supporting it as userdb isn't yet implemented. I think I'll make some generic caching thingy, so that if passdb is same as userdb, they both could be queried from database in one query. Probably by allowing pass_query/pass_filter to return them.