Implement a complete set of integer division operator pairs.

Implement a complete set of integer division operator pairs.

Given a numerator n and a denominator d, each operator pair computes
an integral quotient q and the induced remainder r = n - d q such
that |r| < |d|.  There are five pairs: ceiling, euclidean, floor,
round, and truncate.  Ceiling, floor, round, and truncate compute the
rounded quotient as their names suggest.  Euclidean division is floor
division for positive denominators, and ceiling division for negative
denominators, so that it exhibits the stronger property 0 <= r < |d|.