PK_ERROR_code_t PK_EDGE_euler_close_zip
(
--- received arguments ---
PK_EDGE_t       edge1,  --- Edge to zip
PK_EDGE_t       edge2   --- Edge to delete
)


This function "zips" two edges together by merging the vertices at either end.


Specific Errors:
    PK_ERROR_edge_not_manifold    edge1 or edge2 is not manifold
    PK_ERROR_edge_not_open        edge1 or edge2 is closed
    PK_ERROR_no_common_vertex     edge1 and edge2 have no common vertex
    PK_ERROR_bad_edge             edge1 and edge2 have both vertices
                                  in common


This function "zips" the two edges together into one. Both edge1 and edge2
must be open, share exactly one vertex and be adjacent around a loop. Both
edges must also be manifold although the vertices need not be manifold.

If edge1 and edge2 are the only edges of their vertex, the right hand side
of edge1 will be zipped up.

Both vertices of edge1 will survive, the vertex of edge2 at the open end of
the zip will be deleted and edge2 will be deleted.

Any geometry on the deleted edge and vertex will also be deleted and the
resulting body will normally be invalid.

The inverse of this function is PK_EDGE_euler_open_zip.