[Spambayes] Proposing to drop use_mixed_combining

[T. Alexander Popiel]

In message:  <LNBBLJKPBEHFEDALKOLCAECHCAAB.tim.one@comcast.net>
             Tim Peters <tim.one@comcast.net> writes:
>Proposing to drop the options:
>
>    use_mixed_combining
>    mixed_combining_chi_weight

Hear!  Hear!

- Alex