fix BC break introduced by #2346 (sebastianbergmann/phpunit#2454)

Author: jhdxr

ext/dom/document.c

@@ -1628,6 +1628,9 @@ PHP_FUNCTION(dom_document_savexml)
 
 	doc_props = dom_get_doc_props(intern->document);
 	format = doc_props->formatoutput;
+	if (format) {
+		options = options | XML_SAVE_FORMAT;
+	}
 
 	buf = xmlBufferCreate();
 	if (!buf) {

ext/dom/tests/DOMDocument_savexml_basic2.phpt

@@ -0,0 +1,33 @@
+--TEST--
+DOM Document: saveXML with createElement and formatOutput
+--CREDITS--
+CHU Zhaowei <jhdxr@php.net>
+--SKIPIF--
+<?php require_once('skipif.inc'); ?>
+--FILE--
+<?php
+$dom = new domDocument('1.0', 'UTF-8');
+$dom->formatOutput = true;
+
+$root = $dom->createElement('root');
+$dom->appendChild($root);
+
+$child1 = $dom->createElement('testsuite');
+$root->appendChild($child1);
+
+$child11 = $dom->createElement('testcase');
+$child11->setAttribute('name', 'leaf1');
+$child12 = $dom->createElement('testcase');
+$child12->setAttribute('name', 'leaf2');
+$child1->appendChild($child11);
+$child1->appendChild($child12);
+
+echo $dom->saveXml();
+--EXPECT--
+<?xml version="1.0" encoding="UTF-8"?>
+<root>
+  <testsuite>
+    <testcase name="leaf1"/>
+    <testcase name="leaf2"/>
+  </testsuite>
+</root>