Issue #1898466 by joelpittet, webthingee, lokapujya, pplantinga, lokeoke, richardj, bdragon, steveoliver, ry5n, tlattimore, Cottser, siccababes, jenlampton, evanbarter, rodrigoaguilera, W1n5t0n45, drupalmonkey, ezeedub | c4rl: Update.module - Convert theme_ functions to Twig.

Issue #1898416 by Cottser, joelpittet, drupalninja99, mikl, drupalmonkey, bradwade, pwieck, ezeedub, kerasai, disasm | c4rl: Filter.module - Convert theme_ functions to Twig.

Issue #2002732 by Froelund, diarmy, drupalmonkey: Improve code maintainability by removing unused local variables - core/includes/update.inc.

Issue #2002730 by Froelund, leanderl, drupalmonkey: Improve code maintainability by removing unused local variables - core/includes/theme.inc.