available parser:
* XMLParser::NQXMLTreeParser * XMLParser::NQXMLStreamParser * XMLParser::XMLTreeParser * XMLParser::XMLStreamParser (fastest) * XMLParser::REXMLStreamParser * XMLParser::XMLScanStreamParser
allows integers greater than 32-bit if true
enable Introspection extension by default
enable marshalling ruby objects which include XMLRPC::Marshallable
enable multiCall extension by default
enable <nil/> tag