upgrades

[Clint Adams]

> The upgrade just means taking a backup and then nuking the environment,
> leaving just the wordlist.db.

So, in practical terms, Debian users will have to do the following for
each database:

1. Stop invocation of bogofilter
2. db4.2_recover -h ~/.bogofilter
3. rm ~/.bogofilter/lockfi* ???
4. cd ~/.bogofilter && rm $(db4.2_archive -h .)

This would leave me with one logfile.