Issue #2164025 by skipyT, pwolanin: Improve security of session ID against DB exposure or SQL injection.

Issue #2169447 by damiankloip, sun, longwave: DX: Supply CacheBackendInterface::CACHE_PERMANENT as Cache::PERMANENT.

Issue #2152231 by rteijeiro, steveoliver, joelpittet, hussainweb, shanethehat, jenlampton, kpa, AnythonyR, EVIIILJ, kgoel, Cottser, dsdeiz, hanpersand: Convert theme_vertical_tabs() to Twig

Issue #2176131 by sun: Database configuration form in installer still uses 'db_prefix' instead of 'prefix'.

Issue #2029537 by Xano, InternetDevels, -enzo- | tsphethean: Replace drupal_sort_weight() with SortArray::sortByWeightElement() and remove drupal_sort_weight().

Revert "Issue #2047633 by dawehner, pwolanin, Xano, amateescu, tim.plunkett: Move definition of menu links to hook_menu_link_defaults(), decouple key name from path, and make 'parent' explicit."

This reverts commit 531fd593.

Issue #2121849 by moshe weitzman: Move chmod.directory and chmod.file out of config and into settings so that file writes are independant of the config system.

Issue #2047633 by dawehner, pwolanin, Xano, amateescu, tim.plunkett: Move definition of menu links to hook_menu_link_defaults(), decouple key name from path, and make 'parent' explicit.

Issue #1979468 by Wim Leers, nod_, pwolanin, longwave, thedavidmeister, jessebeach, larowlan | catch: .active from linkGenerator(), l() and theme_links() forces an upper limit of per-page caching for all content containing links.

Somehow this broke PHPUnit, so rolling back for now.

This reverts commit 91b465bd.

Issue #1862202 by plach, Berdir, katbailey, ParisLiakos, alexpott, chx, sun, larowlan, Gábor Hojtsy, cosmicdreams, vijaycs85, YesCT, penyaskito, andypost, Albert Volkman, joelpitett: Objectify the language system.

Issue #1649780 by effulgentsia, jibran, Wim Leers, nod_, hefox, joelpittet, kaare, BarisW, sun, rbayliss, Cottser, fubhy: Remove first/last/odd/even classes in favor of CSS3 pseudo selectors.

Issue #2164597 by longwave, StephaneQ, emok: Doxygen @return tag missing for drupal_render_children.

Issue #2155701 by sun: Installer starts with fatal error/exception 'table 'semaphore' not found' if settings.php contains  already.

Issue #2171015 by alexpott: Drupal 8 HEAD broken: installing Language module fails, after that cannot install any other module.

Issue #2166065 by alexpott, mtift: Replace config_install_default_config with ConfigInstaller service.

Issue #2098119 by beejeebus, alexpott, chx: Replace config context system with baked-in locale support and single-event based overrides.

Issue #2042807 by tim.plunkett, pwolanin, ianthomas_uk, jhodgdon: Convert search plugins to use a ConfigEntity and a PluginBag.

Issue #2168113 by penyaskito, jessebeach, catch: Add leading underscore and other discouragement to drupal_add_css() and drupal_add_js().

Revert "Issue #1979468 by Wim Leers, pwolanin, nod_, thedavidmeister, larowlan: .active from linkGenerator(), l() and theme_links() forces an upper limit of per-page caching for all content containing links."

This reverts commit 624296e7.

Issue #1979468 by Wim Leers, pwolanin, nod_, thedavidmeister, larowlan: .active from linkGenerator(), l() and theme_links() forces an upper limit of per-page caching for all content containing links.