[dovecot] 0.99.3 released

OK, this one will be the final release for a while, I promise (or hope). Fixes mbox corruption when expunging mails from the middle of mailbox with mail_read_mmaped=no which is the default. This bug was already in 0.99.0 release.

I had been using Dovecot like that for 5 days or so without noticing the bug.. Wonder if I lost any mails.