/*
   * find node within tree
   * a NULL passed as 'ns' (namespace) is treated as wildcard
   *
   * call-seq:
   *  node.find("namespace", "name") -> String # recursive
   *  node.find("namespace", "name", 0) -> String # non-recursive
   *
   */
  WsXmlNodeH find( const char *ns, const char *name, int recursive = 1) {