Fixed root class warning in a way that works on both Mac OS X and GNUstep with Clang 3.3

git-svn-id: http://svn.gna.org/svn/etoile/trunk/Etoile/Frameworks/EtoileFoundation@10482 7b3f36aa-e6db-49c1-8b4c-66eac1997e64