COObject: switch to pointer equality. The CoreObject and EtoileUI test suite passes (minus the NSCell test that always failed on 10.9)

git-svn-id: http://svn.gna.org/svn/etoile/trunk/Etoile/Frameworks/CoreObject@10599 7b3f36aa-e6db-49c1-8b4c-66eac1997e64