Merge branch '2.4' into 2.5

* 2.4:
  fix typos
  [HttpKernel] add use statement for phpdoc
  Disabled the PHPUnit self-update on Travis
  [ClassLoader] simplified phpdoc
  [ClassLoader] Add a __call() method to XcacheClassLoader
  fix some minor typos in tests
  [Yaml] fixed mapping keys containing a quoted #
  Added fixture to test parsing of hash keys ending with a space and #
  [Filesystem Component] mkdir race condition fix #11626
  [Validator] reverted permissions change on translation files
  Fixed Factory services not within the ServiceReferenceGraph.
  [CssSelector] Fix URL to SimonSapin/cssselect repo
  [Validator] Fixed wrong translation keys/messages for Collection constraint. The error messages for a missing field and an unexpected field did not match the Contraint class
  [YAML] resolve variables in inlined YAML
  Disallow abstract definitions from doctrine event listener registration

Conflicts:
	src/Symfony/Component/Process/Tests/SigchildDisabledProcessTest.php
	src/Symfony/Component/Yaml/Inline.php

Author: fabpot

EventListener/SessionListener.php

@@ -48,7 +48,7 @@ public static function getSubscribedEvents()
     /**
      * Gets the session object.
      *
-     * @return SessionInterface|null A SessionInterface instance of null if no session is available
+     * @return SessionInterface|null A SessionInterface instance or null if no session is available
      */
     abstract protected function getSession();
 }

EventListener/TestSessionListener.php

@@ -78,7 +78,7 @@ public static function getSubscribedEvents()
     /**
      * Gets the session object.
      *
-     * @return SessionInterface|null A SessionInterface instance of null if no session is available
+     * @return SessionInterface|null A SessionInterface instance or null if no session is available
      */
     abstract protected function getSession();
 }