keep all observers in the list if the 'apply' function you specify
returns void.
git-svn-id: svn+ssh://src.earth.threerings.net/narya/trunk@4374 542714f4-19e9-0310-aa3c-eee0fc999fb1
Made ObserverList work with a passed-in function, actionscript style.
I might reconsider some earlier decisions to go away from ObserverList.
git-svn-id: svn+ssh://src.earth.threerings.net/narya/trunk@3952 542714f4-19e9-0310-aa3c-eee0fc999fb1