[aprssig] Deprication/abandonment of the X1J exception

[Bob Bruninga]

Lynn:
> In  my 3 years of inspecting non-parsed APRS packets, 
> I've never seen a single instance of this X1J 
> exception from the APRS-IS... I would actually be
> relieved it were to go away.

Steve: 
> It is not implemented on findU. If anyone has used 
> it in the last decade they did not check their posit 
> on findU.

Thanks!  Consider it DONE.  I have updated the APRS11 addendum and have emailed Kenwood and Yaesu.  I assume all other authors are reading this on APRSSSIG and can eliminate this code if then want to.

Bob, Wb4APR