[exim] BATV Router

I'm trying to set up a very basic BATV implementation. I have the
redirect router working return signed addresses to their original state.
I also have a transport that will sign the return-path of outbound SMTP
deliveries. Both of these were pretty much copied from the spec.txt
minus the SQL queries.

I tried running the signing on all outbound messages, but that is no
good (obviously after I thought about it for a minute). I still do want
to sign everything I can (I'll exclude problems as they appear). What I
guess I need is a router that uses the external_smtp_batv transport when
delivering a message that has a return-path @ one of my local_domains.

Thanks,
Chris