[Spambayes] dbm on windows, hopefully for the last time

[Skip Montanaro]

    Neale> What do you all think of this: new option "dbm_type" which can be
    Neale> "best", "db3hash", "dbhash", "gdbm", or "dumbdbm".  If it's
    Neale> "best", then the best available dbm implementation will be used.
    Neale> Note that "best" on Windows excludes "dbhash".

Looks like a winner to me.

Skip