Merge branch '5.2' into 5.x

* 5.2: (23 commits)
  [Console] Fix Windows code page support
  [SecurityBundle] Allow ips parameter in access_control accept comma-separated string
  [Form] Add TranslatableMessage support to choice_label option of ChoiceType
  Remove code that deals with legacy behavior of PHP_Incomplete_Class
  [Config][DependencyInjection] Uniformize trailing slash handling
  [PropertyInfo] Make ReflectionExtractor correctly extract nullability
  [PropertyInfo] fix attribute namespace with recursive traits
  [PhpUnitBridge] Fix tests with `@doesNotPerformAssertions` annotations
  Check redis extension version
  [Security] Update Russian translations
  [Notifier] Fix return SentMessage then Messenger not used
  [VarExporter] Add support of PHP enumerations
  [Security] Added missing Japanese translations
  [Security] Added missing Polish translations
  [Security] Add missing Italian translations #41051
  [Security] Missing translations pt_BR
  getProtocolVersion may return null
  Fix return type on isAllowedProperty method
  Make FailoverTransport always pick the first transport
  [TwigBridge] Fix HTML for translatable custom-file label in Bootstrap 4 theme
  ...

Author: nicolas-grekas

Request.php

@@ -1502,7 +1502,7 @@ public function isMethodCacheable()
      * if the proxy is trusted (see "setTrustedProxies()"), otherwise it returns
      * the latter (from the "SERVER_PROTOCOL" server parameter).
      *
-     * @return string
+     * @return string|null
      */
     public function getProtocolVersion()
     {