Issue #2990118 by amateescu: Optimize 'initial' and 'initial_from_field' handling in MySQL and PostgreSQL

(cherry picked from commit bc328489)

Issue #2966523 by alexpott, blakemorgan, almaudoh, gapple, Mixologic, amateescu, bojanz: MySQL 8 Support

(cherry picked from commit 3c106b9f789eb3734f4b65db12dae34754322c82)

Issue #2616724 by amateescu, daffie: Warn when trying to create a database table with a NOT NULL => FALSE primary key

Issue #2974722 by tstoeckler, daffie, amateescu, alexpott, mondrake: Fix dropping of columns in a composite primary key on MariaDB >=10.2.8 and make it consistent across database drivers

Issue #2881522 by mondrake, tstoeckler, daffie, alexpott, amateescu, catch: Add a Schema::findPrimaryKeyColumns method to remove database specific logic from test

Issue #2849669 by alexpott, pwolanin, Munavijayalakshmi, dawehner: Fix \Drupal\Component\Utility\Unicode() because of the Symfony mbstring polyfill

Issue #2951242 by alexpott, amateescu, bmunslow, Berdir, greg606, donaldp: Allow BaseFieldDefinition::setInitialValueFromField() to set a default value - this fixes issues with block_content_update_8400()

Issue #2615496 by amateescu, joseph.olstad, amcgowanca, alexpott, Fabianx, djdevin, greggles, tstoeckler: A serial/primary key field can not be added to an existing table

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 #2791375 by shashikant_chauhan: Fix $tableInformation documentation in pgsql and mysql schema.php

Issue #2753475 by amateescu, timmillwood: Support using the values of another field as initial values when adding a new field

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

Issue #2594845 by er.manojsharma, tarekdj, snehi, dpopdan, anil280988, jhodgdon, cilefen: Many database driver classes have no class doc blocks

Issue #2489672 by pwolanin, mpdonadio, zniki.ru, bzrudi71, Crell: Limit all DB drivers to executing single statements by checking for delimiter

Issue #2554241 by neclimdul: mysql's Schema implementation can only provide information about the default connection

Issue #2537928 by stefan.r, dawehner, alexpott, webflo, jhedstrom: MySQL index normalization only works on table create

Issue #1392754 by tss, justAChris, jhodgdon: Comply with new documentation standards for @file for namespaced class files

Issue #1314214 by stefan.r, phayes, ergophobe, YesCT, damienwhaley, kbasarab, Tor Arne Thune, basic, pfrenssen, yannickoo, simolokid, fietserwin, bzrudi71: MySQL driver does not support full UTF-8 (emojis, asian symbols, mathematical symbols)

Revert "Issue #1314214 by stefan.r, phayes, ergophobe, YesCT, damienwhaley, Tor Arne Thune, kbasarab, pfrenssen, basic, yannickoo, simolokid: MySQL driver does not support full UTF-8 (emojis, asian symbols, mathematical symbols)"

This reverts commit b105158a.

Issue #1314214 by stefan.r, phayes, ergophobe, YesCT, damienwhaley, Tor Arne Thune, kbasarab, pfrenssen, basic, yannickoo, simolokid: MySQL driver does not support full UTF-8 (emojis, asian symbols, mathematical symbols)

Issue #1923406 by stefan.r, yannickoo, catch, Crell, amateescu, pwolanin, morgantocker, Damien Tournoud, sun: Use ASCII character set on alphanumeric fields so we can index all 255 characters

Revert "Issue #1923406 by stefan.r, yannickoo: Use ASCII character set on alphanumeric fields so we can index all 255 characters"

This reverts commit ac4e35ce.

Issue #1923406 by stefan.r, yannickoo: Use ASCII character set on alphanumeric fields so we can index all 255 characters

Issue #1224892 by iaine, lapistano, LinL, jonvk: Duplicate code in mysql/schema.inc (createKeySql = createKeysSqlHelper)

Issue #2232425 followup by danblack, stefan.r: Fixed Database Schema field/column default value is not properly quoted via PDO::quote().

Issue #2297993 by cilefen, marthinal, ivanjaros: Fixed MySQL column and table comments are not truncated properly.

Issue #2232425 by danblack: Database Schema field/column default value is not properly quoted via PDO::quote().

Issue #2060813 by legolasbo: Remove Unused local variable $info from /core/lib/Drupal/Core/Database/Driver/mysql/Schema.php.

Issue #1167144 by chx, catch, claudiu.cristea: Make cache backends responsible for their own storage.

Issue #1891728 by gielfeldt: Fixed DatabaseSchema_mysql()::getComment() does not work for targets other than 'default'.

Issue #780304 by Crell, naxoc, zyxware: Fixed HTML encoding of em wrappers for database table names while showing schema errors.