@Override
    protected <T> void writeTo(OutputStream out, T message, Schema<T> schema) throws IOException
    {
        XmlXIOUtil.writeTo(out, message, schema, buf());
    }
Test xml ser/deser for runtime {@link Map} fields.

@author David Yu
@created Jan 22, 2011
protostuff-xml/src/test/java/io/protostuff/XmlXRuntimeMapTest.java