[aprssig] APRS destination address for a new client software

[Robert Bruninga]

At the request of Frank Olaf <frankose at ifi.uio.no>,
the TOCALL of APCLXX  has been added to the
APRS TOCALL spec for APRS-Cellular applications.
He will manage that number series.
http://www.ew.usna.edu/~bruninga/aprs/tocalls.txt

Bob, WB4APR