 ddns.pl
 written by Stephen Carville 
 Copyright 1999 and licensed under The Gnu Public License V2 or later
 The procedure here is simple.   
  If a record has been added since the last change, delete any previous
  mentions and add a new record. This can lead to expired records but this
  should not be a problem.
 v0.11 -- added domain name to machine name.  nsupdate only works sometimes
          without this
          added CR's between update command blocks.
 v0.15 -- Ok, we do need to delete expired leases.
 v0.16 -- added checkname() to eliminate bad names from getting into DNS.
          nsupdate will send them and DNS will accept them (!)but on a 
	  restart DNS will conk out
 v0.50 -- several changes rolled into one here.
	  Added a provision for extra filters to be defined.
          Enabled a workaround for the nasty behavior of some windows clients.
          Some Windows clients will grab an extra address or two using bogus 
 	     Ethernet addresses.  I added a filter that will keepthse from 
	     being added to the DNS file.
 	  Minor bug fixes  
	  
