Also, for 4.0 i think we should go a step further and remove all this Set<?>/Set<Object> crap/instanceof/copying
instead stopfilter, etc should just take chararrayset, and this is what makestopset should return.
I'll update the patch. for 3.x we can just deprecate the two confusing nuked' ctors from the first patch above...
so we can still make some improvement there.