ln3 Method - Not

Description
Invert the bits of the large number.  This function does essentially the same thing that the ~ operator does, but operates on the large number in place.
Signature
ln& Not ( void )
Parameters
( none )
Returns
( ln & )  A reference to the current large number.
Example
Invert the bits of the variable X, and print the inverted value:
ln X;
...
cout << X.Not( ) << endl;
Notes
It is not clear what the not method (and the ~ operator) should do in the context of a large number.  Should it invert all bits in the large number (up to the maximum number of multi-precision digits), or should it only invert the bits in the multi-precision digits used by the current value?  This implementation does the later, although this leads to the confusing situation where ~0 = 0.  This issue needs to be resolved.