Implements reference counting to track concurrent references to itself.

An object of this type arranges automatic destruction of itself when the final reference is removed.

A reference counting object is any object which has CObject as its base class. Constructing a CObject derived type or calling its Open() member function adds a reference to that object by adding one to the reference count; calling its Close() member function removes a reference by subtracting one from the reference count; when the last user of the object calls Close(), the reference count becomes zero and the object is automatically destroyed.