Merge remote-tracking branch 'core/8.x' into 8.x

core/includes/unicode.inc

core/modules/aggregator/aggregator.admin.inc

core/modules/aggregator/aggregator.install

core/modules/aggregator/aggregator.module

core/modules/aggregator/aggregator.test

core/modules/book/book-node-export-html.tpl.php

core/modules/filter/filter.module

core/modules/locale/locale.install

core/modules/openid/openid.inc

core/modules/openid/openid.module

core/modules/openid/openid.test

core/modules/openid/tests/openid_test.module

core/modules/system/system.base-rtl.css

core/modules/system/system.base.css