This reverts commit cc84f390 - bad
commit message.

Issue #2080391 by johnmcc, Bladedu, chertzog, jeroen12345: Remove Unused local variables from multiple core files.

Issue #2061967 by Maxis, sergeypavlenko, m1r1k: Remove calls to deprecated global  in overlay module.

Issue #2049207 by dlu, blakehall, janstoeckler, ramlev, Moderate | Cottser: Replace .tpl.php with .html.twig in documentation.

Issue #2062009 by InternetDevels: Replace user_access() calls with ->hasPermission() in overlay module.

Issue #1847002 by tim.plunkett, effulgentsia, msonnabaum: Move entity type classes from Drupal$provider\Plugin\Core\Entity to Drupal$provider\Entity.

Issue #2045923 by drupalrv, tim.plunkett: Replace all module_invoke_all() deprecated function calls in procedural code.

Issue #1788888 by jsacksick, David_Rothstein: Fixed Overlay at admin/modules closes on submitting the form.

Issue #1978938 by sidharthap, disasm, laurentchardin, pguillard, dawehner, somepal: Convert overlay_user_dismiss_message() to a Controller.

Issue #1668866 by ParisLiakos, aspilicious, tim.plunkett, pdrake, g.oechsler, dawehner, Berdir, corvus_ch, damiankloip, disasm, marcingy, neclimdul: Replace drupal_goto() with RedirectResponse.

Issue #1363112 by mparker17, mgifford, tlattimore, Jacine, dcmouyard, bowersox, ry5n, ahdiaz: Simplify names of 'element-x' helper classes.

Issue #2011108 by rbayliss, chrisguindon | DmitryDrozdik: Replace drupal_container() with Drupal::service() in the overlay module.

Issue #2012836 by tim.plunkett: Replace drupal_region_class() with direct calls to drupal_html_class().

Issue #1825332 by Berdir, ParisLiakos, andypost, dawehner, jrglasgow, aspilicious: Introduce an AccountInterface to represent the current user.

Issue #1987408 by chrisjlee, jstoller, gnuget, Cottser: Overlay.module - Convert theme_ functions to Twig.

Issue #1987066 by Kevin Morse, JohnAlbin, rteijeiro, echoz, ry5n: Rename files to match CSS file naming convention.

Issue #1818570 by Berdir, effulgentsia, das-peter, andypost: Convert users to the new Entity Field API.

Issue #1898436 by chrisjlee, joelpittet, gnuget, Cottser: overlay.module - Convert PHPTemplate templates to Twig.

Issue #1987426 by shanethehat, Cottser, intergalactic overlords, mr.baileys: Convert maintenance-page.tpl.php to Twig.

Issue #1938430 by shanethehat, steveoliver, Fabianx: Don't add a default theme hook class in template_preprocess().

Issue #1927608 by EclipseGc, tim.plunkett, effulgentsia: Remove the tight coupling between Block Plugins and Block Entities.

Issue #1913618 by tim.plunkett, amateescu: Convert EntityFormControllerInterface to extend FormInterface.

Issue #1959306 by jessebeach: Drupal.announce does not handle multiple messages at the same time; Improve the utility so that simultaneously calls are read.

Issue #1913086 by jessebeach, Wim Leers, mgifford, nod_: Generalize the overlay tabbing management into a utility library.

Issue #1848210 by dysrama, David_Rothstein, kid_icarus, YesCT, Gábor Hojtsy: Fixed [Regression] Submitting a form in Overlay shows content + dsm() for a split second before redirecting to front-end theme.

Issue #1847084 by jessebeach, trawekp, LewisNyman, nod_, tarekdj: Fixed Vertical toolbar doesn't work with overlay (measure/track displacing elements better + provide change events for them).

Issue #967566 by Letharion, mariusz.slonina, indytechcook, adnasa, joestewart, oriol_e9g, Fabianx, tim.plunkett, valthebald, tsvenson, rbayliss, sun, xjm | DocuAnt: Several important Core User settings need to implement hook_field_extra_fields().