unified return null usages
Merge branch '2.3' into 2.4

* 2.3:
  Textarea value should default to empty string instead of null.
  Fix doc blocks
  [Process] Fix #10681, process are failing on Windows Server 2003
  [Security] fix DBAL connection typehint
  [HttpFoundation] status 201 is allowed to have a body
  unified return null usages

Conflicts:
	src/Symfony/Component/Console/Helper/DescriptorHelper.php
	src/Symfony/Component/DependencyInjection/ContainerBuilder.php
	src/Symfony/Component/Finder/Tests/Iterator/RecursiveDirectoryIteratorTest.php
	src/Symfony/Component/Form/Extension/Core/DataTransformer/IntegerToLocalizedStringTransformer.php
	src/Symfony/Component/HttpKernel/Fragment/InlineFragmentRenderer.php