ConstPolyIter:
	A PolyIter which is constructed of a const Poly.

DirPolyIter:
	Provides an iterator for a Poly which can go forward and backwards.

Edge:
	A side of a polygon consisting of two Point's. I'm afraid this one
	is no longer used.

NodePEdge:
	Represents an edge from a Poly.

Point:
	A 2-D point. Some arithmetic operations are overloaded.

PointList:
	List of Point's. I'm afraid that this one is no longer used.

PointListIter:
	An iterator for a PointList.

Poly:
	A polygon. Consist of a double linked list of PolyNode's.

PolyIter:
	Provides an iterator over a Poly.

PolyNode:
	A single point in a Poly.

PosAdder:
	A 'boolean' which can have the values UnKnown, True and False.

Set:
	A template implementation of a Set. Main design issue: fast to
	implement :-)

SetIter:
	Iterator for a Set.

RSet, RSetIter: 
	Similar to the Set classes, but handle data by reference.