Bin: Those members provide a means of checking that you are not casting a random memory address to a pointer to an instance of the base class. Doing that could lead to some bad things happening, so it is a protection against that.
Szigeti: your compile error is not related to this submission.
Fernando: the error you get seems self explanatory. You need to make sure class_handle.hpp, which comes with this submission, is in the same folder as the cpp file being compiled.