Issue #2776975 by joelpittet, dawehner, tim.plunkett, xjm, pfrenssen: March 3, 2017: Convert core to array syntax coding standards for Drupal 8.3.x RC phase

Issue #2665992 by alexpott, klausi, heykarthikwithu, xjm, tstoeckler: @file is not required for classes, interfaces and traits

Issue #2570355 by Sutharsan, stefan.r, kgoel, josephdpurcell, joelpittet, justAChris, dawehner, pfrenssen, pwolanin, David_Rothstein, catch: Replace remaining !placeholder and @placeholder with :placeholder for URLs

Issue #2557519 by alexpott, joelpittet: Remove many usages SafeMarkup::checkPlain() and replace with Html::escape()

Issue #2457887 by prateekMehta, stefan.r, rpayanm, alexpott: Use Utility\SafeMarkup class instead of Utility\String for placeholder(), checkPlain(),format() functions

Issue #2212069 by Gábor Hojtsy, pjonckiere, rteijeiro, cilefen: Non-English Drupal sites get default configuration in English, edited in English, originals not actually used if translated

Issue #2023091 by djevans, badrange: Drupal does not allow W3C compliant language codes where you target a numeric region

Issue #2340667 by YesCT, Pedro Lozano, alexpott, martin107: Protect Drupal\Core\Language\Language::id, and use getId().

Issue #2337825 by YesCT, martin107, mon_franco: Update comment references to the interface for ConfigurableLanguage class due to the ConfigurableLanguageInterface (followup).

Issue #2336177 by alexpott, YesCT: Fixed ConfigurableLanguage cannot be created/removed directly, integrate language_save() and language_delete().

Issue #2308821 by tim.plunkett: Replace FormErrorInterface with $form_state->setErrorByName() and $form_state->setError().

Issue #2246665 by jaredsmith, martin107, YesCT, filijonka, tstoeckler: Typehint with Drupal\Core\Language\LanguageInterface instead Drupal\Core\Language\Language.

Issue #2254495 by ParisLiakos, alexpott: Move language_admin_predefined_list to ConfigurableLanguageManager.

Issue #2196901 by divesh.kumar, longwave: Convert all calls & docs references to check_plain() in core to Drupal\Component\Utility\String::checkPlain() in language module.

Issue #2145007 by tim.plunkett, h3rj4n: Convert form_set_error() in FormBase classes to use FormErrorInterface.

Issue #2003592 by andypost, mhagedon, webflo: Convert language_admin_add_form() and language_admin_edit_form() to a Controllers.