Unit tests

Incidentally, to exercise the PYTHON_OBJECT class hierarchy and flush out any obvious bugs, we developed a testing unit for many of the classes using the excellent "EiffelUnit" unit testing framework produced by Jim Weirich. To run these tests, you will need to install EiffelUnit (I used version 1.0) and execute the "eunit" testing program in the production/eiffel-src/test directory.