partial conversion to BDB 4.2.52?

[Andreas]

I just recompiled cyrus-imapd-2.1.16 and cyrus-sasl-2.1.15 with BDB 4.2
support and it seems to be working. Email is working, delivery, mail clients
ok, etc.

There is a small odd thing, though. /var/lib/imap/db seems to still be at
BDB 4.1, while the rest is at 4.2 (/var/lib/imap/mailboxes.db, for example):

pandora [/var/lib/imap] > db4.2_archive -al
/var/lib/imap/log.0000000001

pandora [/var/lib/imap/db] > db4.2_archive -al
db_archive: Program version 4.2 doesn't match environment version
db_archive: Ignoring log file: log.0000000001: unreadable log version 7
/var/lib/imap/db/log.0000000001
/var/lib/imap/db/log.0000000002


db_archive from BDB 4.1 works in /var/lib/imap/db:

pandora [/var/lib/imap/db] > db4.1_archive -al
/var/lib/imap/db/log.0000000001

pandora [/var/lib/imap/db] > db4.1_archive -as
/var/lib/imap/deliver.db
/var/lib/imap/mailboxes.db


And does not work in /var/lib/imap:

pandora [/var/lib/imap] > db4.1_archive -al
db_archive: Ignoring log file: log.0000000001: unsupported log version 8
db_archive: Invalid log file: log.0000000001: Invalid argument
db_archive: PANIC: Invalid argument
db_archive: PANIC: DB_RUNRECOVERY: Fatal error, run database recovery
db_archive: open: DB_RUNRECOVERY: Fatal error, run database recovery


I know the transaction log file format has changed, so db_archive from 4.1
shouldn't work, that's ok. What bothers me is that the database environment
in /var/lib/imap/db is still at BDB 4.1. Even after archiving all the log files
and shutting the server down (so that /var/lib/imap/db is empty), when I start
it up again it's again at BDB 4.1. Any hints? Should it work, am I doing something
wrong? I already ran db_recover (from 4.1 and 4.2, didn't seem to help).