Merge branch '3.4' into 4.2

* 3.4:
  [FrameworkBundle] Update the xsd to match the actual session configuration
  [Form] CsrfValidationListener marks the token as invalid if it is not a string
  [VarDumper] Fixed phpDoc
  [PhpUnitBridge] fix PHP  5.3 compat
  [Filesystem] Fixed some docblocks and typos
  bumped Symfony version to 3.4.23
  updated VERSION for 3.4.22
  update CONTRIBUTORS for 3.4.22
  updated CHANGELOG for 3.4.22
  fix some minor typos
  do not overwrite the constraint being evaluated

Author: nicolas-grekas

Resources/config/schema/symfony-1.0.xsd

@@ -121,6 +121,7 @@
         <xsd:attribute name="gc-probability" type="xsd:string" />
         <xsd:attribute name="use-strict-mode" type="xsd:boolean" />
         <xsd:attribute name="save-path" type="xsd:string" />
+        <xsd:attribute name="metadata-update-threshold" type="xsd:nonNegativeInteger" />
     </xsd:complexType>
 
     <xsd:complexType name="request">