Merge branch '4.0'

* 4.0:
  [Form] Fixed ContextErrorException in FileType
  [DI] Fix handling of inlined definitions by ContainerBuilder
  [Security] remove unused variable
  [DI] Fix infinite loop when analyzing references
  [Lock][Process][FrameworkBundle] fix tests
  Display a nice error message if the form/serializer component is missing.
  [SecurityBundle] providerIds is undefined error when firewall provider is not specified
  [SecurityBundle] providerIds is undefined error when firewall provider is not specified
  [SecurityBundle] providerIds is undefined error when firewall provider is not specified
  Force phpunit-bridge update (bis)
  [Bridge/PhpUnit] Fix disabling global state preservation
  Incorrect dot on method loadChoices in upgrade doc

Author: nicolas-grekas

Tests/Store/MemcachedStoreTest.php

@@ -26,7 +26,10 @@ public static function setupBeforeClass()
     {
         $memcached = new \Memcached();
         $memcached->addServer(getenv('MEMCACHED_HOST'), 11211);
-        if (false === $memcached->getStats()) {
+        $memcached->get('foo');
+        $code = $memcached->getResultCode();
+
+        if (\Memcached::RES_SUCCESS !== $code && \Memcached::RES_NOTFOUND !== $code) {
             self::markTestSkipped('Unable to connect to the memcache host');
         }
     }