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

core/includes/bootstrap.inc

core/includes/common.inc

core/includes/install.core.inc

core/includes/install.inc

core/includes/mail.inc

core/includes/module.inc

core/includes/schema.inc

core/lib/Drupal/Core/Mail/MailInterface.php

core/lib/Drupal/Core/Mail/PhpMail.php

core/lib/Drupal/Core/Mail/VariableLog.php

core/misc/autocomplete.js

core/modules/aggregator/aggregator-summary-item.tpl.php

core/modules/aggregator/aggregator.module

core/modules/aggregator/aggregator.pages.inc

core/modules/filter/filter.module

core/modules/filter/filter.test

core/modules/node/node.api.php

core/modules/poll/poll.module

core/modules/rdf/rdf.module

core/modules/simpletest/drupal_web_test_case.php