Also, replaces the old animation with the same as in the mobile skin. Bug: T56307 Change-Id: Ida98e080dd26b0354884eee2af3269c6228e3a75
This is the final step of the process described at <https://www.mediawiki.org/wiki/Separating_skins_from_core_MediaWiki>. Corresponding core change: Idfc38503. Change-Id: I84fcf7ce6385b8323544cafe6912a00f1886d20d