PK_ERROR_code_t    PK_LOOP_euler_make_edge
(
--- received arguments ---
PK_LOOP_t          loop,        --- Loop in which to create the edge
PK_FIN_t           fin,         --- Fin to create edge at

--- returned arguments ---
PK_VERTEX_t *const new_vertex,  --- New vertex created
PK_EDGE_t   *const new_edge     --- New edge created
)


This function adds a new edge to a loop.


Specific Errors:
    PK_ERROR_fin_not_in_loop    fin is not in loop
    PK_ERROR_edge_is_ring       there are no vertices in loop


This function adds a trailing edge and vertex to the vertex of fin.  The
direction of new_edge will be towards new_vertex.

loop may be isolated, in which case fin should be PK_ENTITY_null.

new_edge and new_vertex will not have any geometry attached and the
resulting body will be invalid.

The inverse of this function is PK_VERTEX_euler_delete.