[aprssig] aprsd on Raspberry PI

[Bill Vodall]

> Why would you want to run aprsd instead of aprsx?

I've had a long history of using a slightly tweaked APRSD for a custom
configuration that was serving some local network traffic as well as
all (dupes included) traffic off the local RF ports to multiple
clients.   I hope to get that working again before looking at the
newer tools.  The new tools are good but I'm not sure they're as
focused on the RF as I need.

Thanks,
Bill, WA7NWP