`pluso``n``m``k`procedure`+o``n``m``k`procedureA goal that unifies two logic variables

`n`and`m`such that the bit-lists they represent sum to`k`when added. Think of this as if you were doing`(define k (+ n m))`, except that it is relational.Example:

(run 1 (q) (let ((a (build-num 4)) (b (build-num 3))) (fresh (n k) (== k a) (== n b) (pluso n q k)))) ; => (1)