private static String[] toInternedArray(Set<String> set) {
        String[] rv = set.toArray(ARRAY_TYPE);
        for (int i = 0; i < rv.length; i++) {
            rv[i] = rv[i].intern();
        }
        return rv;
    }
This does not extend XMLFilterImpl, because XMLFilterImpl constructor overwrites 
handlers on the wrapped XMLReader.

@version $Id$
@author hsivonen
src/nu/validator/xml/NamespaceDroppingXMLReaderWrapper.java