Issue #2937853 by idebr, mfernea, SherFengChong, alexpott, borisson_: Fix 'Drupal.Formatting.MultipleStatementAlignment' coding standard

(cherry picked from commit 6c40e077)

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

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 #936316 by vaplas, johns996, aerozeppelin, mgifford, gapple, gnuget: CSS aggregation strips some essential whitespace within strings

Issue #2572777 by andypost, alexpott, attiks, andriyun: Fix 'Squiz.Strings.ConcatenationSpacing' coding standard

Issue #2707641 by alexpott, anoopjohn: Ensure core compliance to Drupal.Commenting.FunctionComment.ParamCommentIndentation (part 2)

Issue #2612334 by NickWilde: Remove dead code in \Drupal\Core\Asset\[Css|Js]Collection[Grouper|Optimizer]

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

Issue #1494670 by Liam Morland, jhedstrom, Wim Leers, mfb: References to CSS, JS, and similar files should be root-relative URLs: avoids mixed content warnings & fewer bytes to send

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

Issue #2279105 by mgifford, nidaismailshah, thedavidmeister, amitgoyal, rpayanm, ameenkhan07, rakhimandhania, jhodgdon: Remove as many "..." and ellipsis characters from the codebase as possible without altering the meaning of text

Issue #1833356 by grendzy: CSS files encoded in UTF-8 with BOM break the design when enabling CSS aggregation

Issue #2400287 by hass, cutesquirrel, borisson_, rteijeiro, pfrenssen, cilefen: Remove all occurences of sourceMappingURL and sourceURL when JS files are aggregated

Issue #2364157 by mpdonadio, dawehner, martin107, Berdir, pcambra, naveenvalecha, tim.plunkett: Replace most existing _url calls with Url objects

Issue #2343661 by larowlan, tim.plunkett | xjm: Rename l() to _l() and url() to _url(), and document replacements.

Issue #2100329 by cosmicdreams: Use \Drupal instead of Drupal to make IDEs and static code analyse tools happy.

Issue #2014851 by hlieberman, Wim Leers: Fixed Drupal CSS preprocessing breaks protocol-relative paths.

Issue #1198904 by jox, das-peter: Fixed drupal_load_stylsheet() does not comply with standards when using @import.

Issue #352951 by Wim Leers, mfer, mcjim, larowlan, RobLoach, sdboyer, Owen Barton, JohnAlbin: Make JS & CSS Preprocessing Pluggable.