Fixed broken notifications on GNUstep due to dispatch_get_main_queue() being 
unsupported.

Note: Until the AppKit includes special support for libdispatch, the solution 
is to use -performSelectorOnMainThread:withObject:waitUntilDone: or similar.


git-svn-id: http://svn.gna.org/svn/etoile/trunk/Etoile/Frameworks/CoreObject@10032 7b3f36aa-e6db-49c1-8b4c-66eac1997e64