Don't use recursion when transferring a DOM internal document pointer (php#16180)

Recursion is typically slower than iteration, and furthermore, this can
cause problems in theory with deep trees.

Author: ndossche

ext/dom/document.c

@@ -1074,7 +1074,7 @@ PHP_METHOD(DOMDocument, getElementById)
 }
 /* }}} end dom_document_get_element_by_id */
 
-static zend_always_inline void php_dom_transfer_document_ref_single_node(xmlNodePtr node, php_libxml_ref_obj *new_document)
+static void php_dom_transfer_document_ref_single_node(xmlNodePtr node, php_libxml_ref_obj *new_document)
 {
 	php_libxml_node_ptr *iteration_object_ptr = node->_private;
 	if (iteration_object_ptr) {
@@ -1087,21 +1087,25 @@ static zend_always_inline void php_dom_transfer_document_ref_single_node(xmlNode
 	}
 }
 
-static void php_dom_transfer_document_ref(xmlNodePtr node, php_libxml_ref_obj *new_document)
+static void php_dom_transfer_document_ref_single_aux(xmlNodePtr node, php_libxml_ref_obj *new_document)
 {
-	if (node->children) {
-		php_dom_transfer_document_ref(node->children, new_document);
+	php_dom_transfer_document_ref_single_node(node, new_document);
+	if (node->type == XML_ELEMENT_NODE) {
+		for (xmlAttrPtr attr = node->properties; attr != NULL; attr = attr->next) {
+			php_dom_transfer_document_ref_single_node((xmlNodePtr) attr, new_document);
+		}
 	}
+}
 
-	while (node) {
-		if (node->type == XML_ELEMENT_NODE) {
-			for (xmlAttrPtr attr = node->properties; attr != NULL; attr = attr->next) {
-				php_dom_transfer_document_ref_single_node((xmlNodePtr) attr, new_document);
-			}
-		}
+static void php_dom_transfer_document_ref(xmlNodePtr node, php_libxml_ref_obj *new_document)
+{
+	xmlNodePtr base = node;
+	php_dom_transfer_document_ref_single_aux(base, new_document);
 
-		php_dom_transfer_document_ref_single_node(node, new_document);
-		node = node->next;
+	node = node->children;
+	while (node != NULL) {
+		php_dom_transfer_document_ref_single_aux(node, new_document);
+		node = php_dom_next_in_tree_order(node, base);
 	}
 }