where the elements are user defined objects that know how to read and
write themselves on a stream. Sets are required to contain elements all of
the same type to make network traffic more efficient (avoid sending the
classname every time an element is added or removed).
git-svn-id: svn+ssh://src.earth.threerings.net/narya/trunk@264 542714f4-19e9-0310-aa3c-eee0fc999fb1
Michael Bayne