Undefining 'dup' and 'clone' for generated classes.

Any generated classes that we want to duplicate or clone will have
their own clone methods defined in the specifications. For example,
Node has clone_node.

Perhaps at some point, we can implement 'dup' and 'clone' for some
classes by rerouting them to the specified cloninig methods. For now,
we'll leave them undefined.
Showing names of user-created classes correctly in the console.