distinctc

added

ns
clojure.core.logic.fd

type
function

(distinctc v*)

The real distinct constraint. v* can be seq of logic vars and
values or it can be a logic var itself. This constraint does not 
run until v* has become ground. When it has become ground we group
v* into a set of logic vars and a sorted set of known singleton 
values. We then construct the individual constraint for each var.