#11 bad exit status for -n and -N

[Ward Wouts]

From the manpage:

In non-passthrough mode: 0 for spam; 1 for
non-spam; 2 for I/O or other errors.

This is very nice for the -t option, it's pretty much
the only way to do that. But when I use the -n or -N
option I only want an exit status >0 when something
goes wrong. (I know it's not spam. I'm telling it, it's
not spam. This is not an error :) )

This is especially anoying on combination with mutt's
wait_key option... (or is that without the wait_key
option) From mutt's manual about wait_key:

When unset, Mutt will wait for a key only if the
external command returned a non-zero status.

So when I use bmf -N (or -n) in a mutt macro that has
wait_key unset it always waits for a key, because of
the non-zero exit status of bmf.