[e2e] back by popular demand - a DNS calculator

[Joe Touch]

Hi, all,

By popular request, I've restored the DNS calculator function as an 
operational service. See:

http://www.isi.edu/touch/tools/dns-calc.html

(this was designed for a Sigcomm OO session, but it's been used several 
places as a good example why the DNS should NOT be anything more than a 
mapping service)

Joe

PS - if you do happen to use it as an example, please do drop me a note; 
I'd be very glad to track that info. and/or include a pointer to the 
classes that use it.