[aprssig] D-STAR formats added to APRS Frequency Object Spec

[Robert Bruninga]

The APRS Frequency Object spec has been updated now to include D-STAR
formats:
http://aprs.org/info/freqspec.txt

This spec has not been updated in several years.  If anyone finds any
other needed edits, please let me know.
Here is the new section on D-STAR:

D-STAR STATION FORMATS:
------------------------

To make a voice call with D-STAR station that uses a D-STAR repeater,
the callsign of the accessing repeater is needed.  On the other hand,
to make a voice call with D-STAR station that does not use a D-STAR
repeater,
the frequency of the station's voice channel is needed.  Here are the
examples for the D-STAR QSY information.

Communication without using a repeater station:
 1) FFF.FFFMHz D-STAR comment...

Communication using a repeater station:
 2) FFF.FFFMHz D-STAR>CALLSN A comment...
 3) D-STAR>CALLSN A comment...

1st 7-BYTES  means D-STAR station format.
2nd 8-BYTES  "CALLSN A" means the callsign of access repeater
             "CALLSN A" is fixed 8 characters.

(The optional "oXXX" (SHIFT/OFFSET) information is available between
 "FFF.FFFMHz" and "D-STAR")

Bob