TestBranch: -testOverriddenIsEqualsObject: add a note that overriding -isEquals: on COObject is no longer allowed. also disable part of the test

git-svn-id: http://svn.gna.org/svn/etoile/trunk/Etoile/Frameworks/CoreObject@10289 7b3f36aa-e6db-49c1-8b4c-66eac1997e64