Issue #2102477 by alexpott: Convert remainder of language negotiation settings to configuration system.
Issue #2164025 by skipyT, pwolanin: Improve security of session ID against DB exposure or SQL injection.
Issue #2172561 by Gábor Hojtsy: Config overrides may spill over to undesired places.
Issue #2164367 by alexpott, tim.plunkett, dawehner: Rebuild router as few times as possible per request.
Revert "Issue #2172561 by Gábor Hojtsy: Config overrides may spill over to undesired places."

This reverts commit f2769f4db32f69a68ad4391d60d3847b9da538e6.
Issue #2181101 by InternetDevels: Update settings tab not visible.
Issue #2172941 by vijaycs85, damiankloip: Endless looping on Config::castValue() for undefined config data type.
Issue #2181811 by alexpott: System info can become inconsistent if hook_system_info_alter() makes a module required.
Issue #2171655 by dawehner: Drupal should not typehint the EventDispatcher directly.
Issue #2172561 by Gábor Hojtsy, alexpott: Config overrides may spill over to undesired places.
Issue #1165694 by pillarsdotnet, Sutharsan, droplet: Remove default nomask from file_scan_directory().
Issue #2175739 by alexpott: Actually test node_access_test_secret_catalan and clean up deprecated code in NodeAccessLanguageTest.
Issue #1898416 follow-up by mparker17, mikl: Remove debug code.
Issue #2182603 by alexpott: Remove LocaleUninstallTest.
Issue #2181293 by pwolanin, dawehner: AccessManager::checkNamedRoute() is not passing all route defaults (or building a complete route request).
Issue #1913510 by erich_s, jibran, scresante, nod_, mitron: Core Javascript Files Not Using Standard Indentation.
Issue #1376122 by sun: Stream wrappers of parent site are leaking into all tests.
Issue #2167109 by Berdir, sun, alexpott, ACF, acrollet, adamdicarlo, Albert Volkman, andreiashu, andyceo, andypost, anenkov, aspilicious, barbun, beejeebus, boombatower, cam8001, chriscalip, chx, cosmicdreams, dagmar, damiankloip, dawehner, deviance, disasm, dixon_, dstol, ebrowet, Gábor Hojtsy, heyrocker, Hydra, ianthomas_uk, japicoder, jcisio, jibran, julien, justafish, jvns, KarenS, kbasarab, kim.pepper, larowlan, Lars Toomre, leschekfm, Letharion, LinL, lirantal, Lukas von Blarer, marcingy, Mike Wacker, mrf, mtift, mtunay, n3or, nadavoid, nick_schuch, Niklas Fiekas, ParisLiakos, pcambra, penyaskito, pfrenssen, plopesc, Pol, Rok Žlender, rvilar, swentel, tim.plunkett, tobiasb, tsvenson, typhonius, vasi1186, vijaycs85, wamilton, webchick, webflo, wizonesolutions, xjm, yched, YesCT, znerol: Remove Variable subsystem.
Issue #2021111 by jibran, tim.plunkett, mtift: Add a ConfigFactoryInterface for ConfigFactory.
Issue #2176141 by sun, chx: Add a return value to file_save_htaccess().