Merge branch '4.4' into 5.1

* 4.4:
  [HttpFoundation] Drop int return type from parseFilesize()
  Added $translator->addLoader()
  bug symfony/symfony#39878 [doctrine-bridge] Add username to UserNameNotFoundException
  fix spelling
  Add check for constant in Curl client
  Revert #38614, add assert to avoid regression
  Fix problem when SYMFONY_PHPUNIT_VERSION is empty string value
  Update PHP CS Fixer config to v2.18

Author: derrabus

README.md

@@ -12,8 +12,10 @@ $ composer require symfony/translation
 
 ```php
 use Symfony\Component\Translation\Translator;
+use Symfony\Component\Translation\Loader\ArrayLoader;
 
 $translator = new Translator('fr_FR');
+$translator->addLoader('array', new ArrayLoader());
 $translator->addResource('array', [
     'Hello World!' => 'Bonjour !',
 ], 'fr_FR');