Issue #1821420 by vijaycs85, cam8001, Albert Volkman, ACF, typhonius, pcambra, Berdir: Convert mail variables to cmi.

Issue #209672 by pillarsdotnet, theborg, penyaskito, cburschka, naxoc, Rob Loach, carlos8f, gdud, olamaekle: Added Use site name in From: header for system e-mails.

Issue #310315 by Waltemath, justafish, naxoc: Fixed drupal_wrap_mail() strips trailing blanks from standard hyphen-hyphen-space-newline e-mail signature separator.

Issue #1754208 by PrabhuG, webflo, savithac, Gábor Hojtsy: Convert hook_mail() and hook_mail_alter() to langcode.

Issue #1711070 by kid_icarus, tim.plunkett, xjm, droplet, zendoodles and cam8001: Convert tests to use ::$modules property instead of parent::setUp($modules).

Using the language_manager wrapper function to return a language whether or not we're in the requet scope

- Patch #1510686 by cosmicdreams, vasi1186, webflo, disasm: replace remaining references to global () with drupal_container().