[aprssig] APRSData + d710 auto tune

[Bill Vodall WA7NWP]

We use the equivalent functionality in Digi_ned quite a bit.  No
D710's in the family yet to stimulate development of a correctly
formatted auto-tuning packet.

Bill - WA7NWP

> I am not sure how many of you still utilize the APRSData program for
> alerting to satellites on APRS, but I use it daily here in Michigan still to
> know when AO-51 or ISS are over horizon.
>