deleting comms/asterisk18

[John Nemeth <jnemeth%cue.bc.ca@localhost>]

     Asterisk 1.8.x was EOLed on October 21st, 2015 (almost three
years ago).  It likely has numerous security holes.  At this point,
nobody should still be using it.  So, I'd like to delete it.

     Another concern is that we are only a little over two years
away from seeing Asterisk 18.x.  Based on the current nameing
pattern, that version would go in the directory comms/asterisk18.
That would be a jump of nine major versions, so the directory needs
to be cleaned out as soon as possible.  If there are no significant
objections, I will do it as soon as the upcoming freeze is over.