Mark zxcvbn global to avoid JSHint errors.

props jorbin.
fixes #25911.

Built from https://develop.svn.wordpress.org/trunk@26111


git-svn-id: http://core.svn.wordpress.org/trunk@26023 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Free common.js of JSHint errors.

props jorbin.
fixes #25912.

Built from https://develop.svn.wordpress.org/trunk@26112


git-svn-id: http://core.svn.wordpress.org/trunk@26024 1a063a9b-81f0-0310-95a4-ce76da25c4cd