It's now possible to have complete flexibility with cancelling bindings,
i.e. it's possible to re-implement all of the other ways to cancel bindings
using the callback.
This sytem has been designed with complete safety in mind:
- It is safe to call the callback more than once (does nothing after the
first call).
- The callback does not expire, and can be stored for as long as
necessary.
- If a callback is returned, there is no other way to cancel the binding
(again, due to safety).
V690 The 'WorldObjectInRangeCheck' class implements a copy constructor, but lacks the the '=' operator. It is dangerous to use such a class. elunautility.h 103
