Merge branch '2.8' into 3.0

* 2.8:
  `@throws` annotations should go after `@return`
  Fix merge
  updated VERSION for 2.3.42
  update CONTRIBUTORS for 2.3.42
  updated CHANGELOG for 2.3.42
  Revert "bug #18908 [DependencyInjection] force enabling the external XML entity loaders (xabbuh)"
  Partial revert of previous PR
  [DependencyInjection] Skip deep reference check for 'service_container'
  Catch \Throwable
  [Serializer] Add missing @throws annotations
  Fix for #18843
  force enabling the external XML entity loaders
  Removed UTC specification with timestamp

Conflicts:
	CHANGELOG-2.3.md
	src/Symfony/Bundle/FrameworkBundle/Routing/DelegatingLoader.php
	src/Symfony/Bundle/TwigBundle/Extension/AssetsExtension.php
	src/Symfony/Component/Config/Loader/FileLoader.php
	src/Symfony/Component/DependencyInjection/Container.php
	src/Symfony/Component/DependencyInjection/ContainerBuilder.php
	src/Symfony/Component/Finder/Expression/Expression.php
	src/Symfony/Component/Finder/Finder.php
	src/Symfony/Component/HttpKernel/DependencyInjection/ContainerAwareHttpKernel.php
	src/Symfony/Component/HttpKernel/HttpCache/HttpCache.php

Author: nicolas-grekas