Twenty Fourteen: changes to JavaScript files to pass `jshint`, props jorbin. Fixes #25908 #25909 #25910.

 * Add global variable flags to top of JS files.
 * Group variable declarations correctly.

git-svn-id: https://develop.svn.wordpress.org/trunk@26084 602fd350-edb4-49c9-b593-d223f7449a82