wpLink: use simpler expressions to detect email address or URL. We are not validating user input here, just suggesting.

see #19992.
Built from https://develop.svn.wordpress.org/trunk@28751


git-svn-id: http://core.svn.wordpress.org/trunk@28565 1a063a9b-81f0-0310-95a4-ce76da25c4cd