[Dovecot] 0.99.11-test6

[Timo Sirainen]

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

I think I've fixed the problems that were corrupting indexes with the 
new code. It happened every time you had expunged some messages and new 
messages arrived. I think this release might actually work :)

disable_plaintext_auth = yes will be default from now on. It allows 
plaintext authentication from localhost (127.*, ::1) however.

I just figured out that the lockless cache file reading prevents me 
from fixing the mbox code to work the same way it used to. I'm not sure 
actually how this would be best fixed.. Problem is that headers in 
mails change and move the messages around in the mailbox, so I have to 
keep track of them. Previously I just updated the header size in index 
files.. but without read locks this can't be done safely.

One possibility would be to parse the whole mbox file every time when 
the mailbox is opened (or when it needs to be read) and save the header 
sizes in memory. That'd make it slower than it is today though..

Or maybe it'd work if I just grabbed exclusive lock whenever reading 
header sizes. They could be then copied into memory to avoid locking 
more than once. But that still creates locking contention if lots of 
clients are reading the mailbox. Exactly in the situation where I'd 
mostly use mboxes..

I could also save it in .imap.index file which still currently uses 
read-locks. But I'd rather want to get rid of them in there too.