To do list for Dynamic DHCP to DNS

Add an MX option to ddnsupdate.pl so MX records can be added or deleted.

Add CNAME option to ddnsupdate.pl

Add option to dnsupdate to change the TTL for an entry

Add some smarts to dnsupdate.pl to avoid adding entries without a legitimate
domain name.

Add code to remove expired entries more proactively. (done)

Add cgi scripts to allow for web based administration of DHCP and DNS (try
webmin!)
