Attaches the given entity to the path with the given name.
A8.13 If an empty name string is given,
the string is set
to the WED name of the path the entity is currently attached to (if any).
If NULL is given for the name, the entity is detached from its previous path.
entity - entity pointer.
name - path name
(STRING* or char*), NULL, or pointer to an empty STRING.
Number of nodes in the path, or 0 if the path was not found.
entity - is attached to or detached from the path.