/*
   * iterate over children
   *
   * See also XmlNode#next
   *
   * XmlNode#each iterates over children, XmlNode#next over siblings
   *
   * can be limited to children with specific name (and specific namespace)
   *
   * for array-like constructs, e.g
   *  <Parent>
   *    <Child>..
   *    <Child>..
   *    <Child>..
   *    <OtherChild>..
   *    <OtherChild>..
   *    <OtherChild>..
   *
   *   doc.Parent.each do |child|
   *     ... iterates over all 6 children ...
   *   end
   *
   * use XmlNode#next as in
   *   node = doc.OtherChild
   *   while node do
   *     ... do something with node ...
   *    node = node.next
   *   end
   *
   * call-seq:
   *  node.each { |XmlNode| ... }
   *  node.each("name") { |XmlNode| ... }
   *  node.each("name", "namespace") { |XmlNode| ... }
   *
   */

  void each(const char *name = NULL, const char *ns = NULL) {