axiom_xml_reader_create_for_memory expects a libxml data type, denying parser independent implemention.

the function axiom_xml_reader_create_for_memory is allowing type AXIS2_XML_PARSER_TYPE_DOC (4th parameter). Under this type its container (2nd Parameter) should be a variable of xmlDoc type. Since this function should be independent from the parser (libxml wrapper or GUTHTHILA) it is been using, it needed to be corrected.