Merge branch '2.3' into 2.7

* 2.3:
  [PropertyAccess] ->getValue() should be read-only
  [Config] Fix XmlUtilsTest namespace
  [Routing] add query param if value is different from default

Conflicts:
	src/Symfony/Component/PropertyAccess/Tests/PropertyAccessorTest.php

Author: nicolas-grekas

Tests/Util/XmlUtilsTest.php

@@ -9,7 +9,7 @@
  * file that was distributed with this source code.
  */
 
-namespace Symfony\Component\Config\Tests\Loader;
+namespace Symfony\Component\Config\Tests\Util;
 
 use Symfony\Component\Config\Util\XmlUtils;