-M inconsistency

[Boris 'pi' Piwinger]

Hi!

I think this is the time to fix an old inconsistency about
the need for -M.

When training with -s or -n, mboxes are autodetected, so -s
and -sM are the same.

When checking a message with -v, -M is needed to get
meaningful output, -v alone treats it as one message which
does not make any sense. AFAICS it is a recent fix that now
only -vvM and -vvvM produce something useful.

Same for -T.

Bogofilter without options on mbox does not make any sense
and hence should produce an error I think.

So what to do? I don't know how autodetection is done, but
it works, so it should also work for -v and -T (-t, -TT).

BTW: -t could also go completely.

pi