Merge remote-tracking branch 'upstream/8.x' into remerge

core/MAINTAINERS.txt

core/includes/form.inc

core/includes/language.inc

core/includes/module.inc

core/lib/Drupal/Core/Cache/NullBackend.php

core/lib/Drupal/Core/Database/Connection.php

core/modules/node/node.module

core/modules/simpletest/lib/Drupal/simpletest/TestBase.php

...modules/simpletest/lib/Drupal/simpletest/UnitTestBase.php

.../modules/simpletest/lib/Drupal/simpletest/WebTestBase.php

core/modules/system/language.api.php

...tem/lib/Drupal/system/Tests/Actions/ConfigurationTest.php

...dules/system/lib/Drupal/system/Tests/Actions/LoopTest.php

.../system/lib/Drupal/system/Tests/Cache/NullBackendTest.php

.../system/lib/Drupal/system/Tests/Common/HtmlToTextTest.php

...odules/system/lib/Drupal/system/Tests/Common/MailTest.php

core/modules/system/system.info