[aprssig] Garmin emulation

[Scott Miller]

> NMEA data.  Maybe later versions will generate the Garmin native
> protocol?  If not, a smart terminal program and the Garmin manual (you
> may have to poke about Garmin's website for the appropriate one that
> details their native protocol, but it is documented) should do the
> job...

I've already got that part working.  My program emulates a Garmin GPS for
testing purposes, and will send and receive position/velocity/time data,
decode waypoints, and so forth.  I just need the virtual serial port program
to avoid tying up two serial ports and a null modem cable.  If it works out,
it'll open up a lot more options for APRS mapping software, even if it's not
totally automated.

Scott
N1VG