Merge branch '3.4' into 4.0

* 3.4: (37 commits)
  Remove some unused variables and properties
  [appveyor] disable memory limit on composer up
  [HttpFoundation] don't prefix cookies with "Set-Cookie:"
  Remove some unused variables and properties
  Fix debug:form definition
  Remove some unused variables, properties and methods
  fix some edge cases with indented blocks
  [ExpressionLanguage] Fix parse error on 5.3
  [HttpKernel] remove noisy frame in controller stack traces
  [DI] Force root-namespace for function calls in the dumper container
  [DI] Fix circular-aliases message
  register system cache clearer only if it's used
  doc : Namespace prefix must end with a "\"
  [ExpressionLanguage] throw an SyntaxError instead of letting a undefined index notice
  Prevent a loop in aliases within the `findDefinition` method
  [HttpKernel] Disable inlining on PHP 5
  Ensure that inlined services with parameterized class name can be dumped
  [DI] Fix non-string class handling in PhpDumper
  Throw a sensible exception when controller has been removed
  Remove LOCK_EX That Breaks Cache Usage on NFS
  ...

Author: nicolas-grekas

Store/MemcachedStore.php

@@ -24,12 +24,6 @@
  */
 class MemcachedStore implements StoreInterface
 {
-    private static $defaultClientOptions = array(
-        'persistent_id' => null,
-        'username' => null,
-        'password' => null,
-    );
-
     private $memcached;
     private $initialTtl;
     /** @var bool */