TestObject: add a test which demonstrates a flaw in the hash stability of COObject. IMO the only reasonable fix is to revert to using pointer equality (NSObject's hash/isEqual:)

git-svn-id: http://svn.gna.org/svn/etoile/trunk/Etoile/Frameworks/CoreObject@10148 7b3f36aa-e6db-49c1-8b4c-66eac1997e64