COLINEAR - determine if edges or vertecies are COLINEAR in triangulated
           model
edgesColinear		see whether or not two edges are colinear
vertexBetweenVertices	determine whether or not a vertex is on a line
                          between two other vertices
Function Prototypes:
int edgesColinear (Edge *e1, Edge *e2);
int vertexBetweenVertices (Vertex *v, Vertex *v1, Vertex *v2);

edgesColinear:
Input:
e1	pointer to first Edge
e2	pointer to second Edge

Returns: (int)
1	if colinear

vertexBetweenVertices:
Input:
v		pointer to first Vertex in question
v1		pointer to first reference Vertex
v2		pointer to second reference Vertex

Returns: integer
1		if v=v1 or v=v2 or if v is between v1 and v2
0		otherwise

Author:  Dave Hale, Colorado School of Mines, Fall 1990.