Merge branch '2.3' into 2.7

* 2.3:
  [HttpFoundation] Fix transient test
  [HttpFoundation] Add a dependency on the mbstring polyfill
  add readme files where missing
  Don't use reflections when possible
  [Form] Update form tests after the ICU data update
  [Intl] Update tests and the number formatter to match behaviour of the intl extension
  [Intl] Update the ICU data to version 55
  [Intl] Fix the update-data.php script in preparation for ICU 5.5
  Use constant instead of function call.
  fixed test name
  automatically generate safe fallback filename

Conflicts:
	src/Symfony/Component/Debug/Debug.php
	src/Symfony/Component/HttpFoundation/composer.json
	src/Symfony/Component/Serializer/Tests/Normalizer/GetSetMethodNormalizerTest.php

Author: nicolas-grekas

Mapping/PropertyMetadata.php

@@ -58,12 +58,11 @@ public function getPropertyValue($object)
      */
     protected function newReflectionMember($objectOrClassName)
     {
-        $class = new \ReflectionClass($objectOrClassName);
-        while (!$class->hasProperty($this->getName())) {
-            $class = $class->getParentClass();
+        while (!property_exists($objectOrClassName, $this->getName())) {
+            $objectOrClassName = get_parent_class($objectOrClassName);
         }
 
-        $member = new \ReflectionProperty($class->getName(), $this->getName());
+        $member = new \ReflectionProperty($objectOrClassName, $this->getName());
         $member->setAccessible(true);
 
         return $member;