[Python-3000] Immutable bytes type and dbm modules

["Martin v. Löwis"]

> IMHO all of that is desirable in many situations but it is not strict.
> bytes:bytes or int:bytes (depending on the database type) are
> fundamentally all the C berkeleydb library knows.  Attaching meaning
> to the keys and values is up to the user.  I'm about to try a _bsddb.c
> that strictly enforces bytes as values for the underlying bsddb.db API
> provided by _bsddb in my sandbox under the assumption that being
> strict about bytes is desired at that level there.  I predict lots of
> Lib/bsddb/test/ edits.

I fixed it all a few weeks ago, in revisions r56754, r56840, r56890,
r56892, r56914. I predict you'll find that most of the edits are
already committed.

Regards,
Martin