module S:Delaunay.CCC
type
val ccw : point -> point -> point -> boolccw p q r states that the
circle through points (p,q,r) is traversed counterclockwise
when we encounter the points in cyclic order p,q,r,p,... *val in_circle : point ->
point -> point -> point -> boolin_circle p q r s states that s lies
inside the circle (p,q,r) if ccw p q r is true, or outside that
circle if ccw p q r is false.