Duplicates the list nodes, and returns the duplicate list.

When you are finished with the list returned, pass it to DeleteNodeList_bn (not the Standard C 'free' or 'delete').

This only makes a copy of the list; if you want to duplicate the nodes as well, use CopyNodes_bn.

When Netica API functions return const nodelist_bn*, the returned node lists are volatile (they may become invalid after further Netica calls) and nonmodifiable. Duplicating them with this function removes both of these concerns.