CircularKernel::ConstructCircularArc_2

A model fo of this type must provide:

CircularKernel::Circular_arc_2
	fo ( CircularKernel::Circle_2 c)
		Constructs an arc from a full circle.
CircularKernel::Circular_arc_2
	fo ( CircularKernel::Circle_2 c, CircularKernel::Circular_arc_point_2 p1, CircularKernel::Circular_arc_point_2 p2)
		Construct the circular arc supported by c, that is oriented counterclockwise, whose source is p1 and whose target is p2. Precondition: p1 and p2 lie on c.
CircularKernel::Circular_arc_2
	fo ( CircularKernel::Circle_2 c, CircularKernel::Circle_2 c1, bool b1, CircularKernel::Circle_2 c2, bool b2)
		Constructs the unique circular arc that is oriented counterclockwise, whose supporting circle is c, and whose source endpoint is the intersection of c and c1 with index $$b1, and whose target is the intersection of c and c2 of index $$b2, where intersections are ordered lexicographically. Precondition: c intersects both c1 and c2, and the arc defined by the intersections has non-zero length.
CircularKernel::Circular_arc_2
	fo ( CircularKernel::Circle_2 c, CircularKernel::Line_2 l1, bool b1, CircularKernel::Line_2 l2, bool b2)
		Same, for intersections defined by lines instead of circles.