Support responsive design meta tags

Backporting them from Drupal 8.

      <meta name="MobileOptimized" content="width" />
      <meta name="HandheldFriendly" content="true" />
      <meta name="viewport" content="width=device-width" />
      <meta http-equiv="cleartype" content="on" />

Related:
#1468582: Add mobile friendly meta tags to the html.tpl.php
#1616896: Revert: "Remove $default_mobile_metatags"
https://github.com/h5bp/html5-boilerplate/issues/824