Add test case in COBranch (-testOverriddenIsEqualsObject) that clearly identifies the problems I've been hitting with COAttributedStringAttribute

git-svn-id: svn://svn.gna.org/svn/etoile/trunk/Etoile/Frameworks/CoreObject@9987 7b3f36aa-e6db-49c1-8b4c-66eac1997e64