Merge branch '3.4' into 4.0

* 3.4:
  [HttpKernel] DebugHandlersListener should always replace the existing exception handler
  fix the Composer API being used
  [Security] Notify that symfony/expression-language is not installed if ExpressionLanguage and ExpressionLanguagePrivider are used
  [Debug] Always decorate existing exception handlers to deal with fatal errors
  Enableable ArrayNodeDefinition is disabled for empty configuration
  Fixing a bug where the dump() function depended on bundle ordering
  [Cache] Fix handling of apcu_fetch() edgy behavior
  Add nn (Norwegian Nynorsk) translation files, and improve existing file
  Problem in phar see mergerequest #25579
  [Form] Disallow transform dates beyond the year 9999
  Avoid button label translation when it's set to false
  Copied NO language files to the new NB locale.
  [Serializer] DateTimeNormalizer handling of null and empty values (returning null or empty instead of new object)
  Fix options resolver with array allowed types
  [Console] Improve phpdoc on StyleInterface::ask()
  [TwigBridge][WIP] Pass the form-check-inline in parent

Author: nicolas-grekas

Style/StyleInterface.php

@@ -91,7 +91,7 @@ public function table(array $headers, array $rows);
      * @param string|null   $default
      * @param callable|null $validator
      *
-     * @return string
+     * @return mixed
      */
     public function ask($question, $default = null, $validator = null);
 
@@ -101,7 +101,7 @@ public function ask($question, $default = null, $validator = null);
      * @param string        $question
      * @param callable|null $validator
      *
-     * @return string
+     * @return mixed
      */
     public function askHidden($question, $validator = null);
 
@@ -122,7 +122,7 @@ public function confirm($question, $default = true);
      * @param array           $choices
      * @param string|int|null $default
      *
-     * @return string
+     * @return mixed
      */
     public function choice($question, array $choices, $default = null);
 

Style/SymfonyStyle.php

@@ -279,7 +279,7 @@ public function createProgressBar($max = 0)
     }
 
     /**
-     * @return string
+     * @return mixed
      */
     public function askQuestion(Question $question)
     {