Merge branch '3.4' into 4.3

* 3.4:
  [FrameworkBundle] Detect indirect env vars in routing
  Remove calls to deprecated function assertAttributeX
  [Intl] Order alpha2 to alpha3 mapping
  [Routing] added a warning about the getRouteCollection() method
  Allow sutFqcnResolver to return array
  [HttpFoundation] Revert getClientIp @return docblock

Author: fabpot

RouterInterface.php

@@ -26,6 +26,9 @@ interface RouterInterface extends UrlMatcherInterface, UrlGeneratorInterface
     /**
      * Gets the RouteCollection instance associated with this Router.
      *
+     * WARNING: This method should never be used at runtime as it is SLOW.
+     *          You might use it in a cache warmer though.
+     *
      * @return RouteCollection A RouteCollection instance
      */
     public function getRouteCollection();