wpLink: bring back the Cancel link, improve responsive styles, see #26952

Built from https://develop.svn.wordpress.org/trunk@27510


git-svn-id: http://core.svn.wordpress.org/trunk@27353 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-includes/js/wplink.js

@@ -38,7 +38,7 @@ var wpLink;
 				event.preventDefault();
 				wpLink.update();
 			});
-			inputs.close.add( inputs.backdrop ).click( function( event ) {
+			inputs.close.add( inputs.backdrop ).add( '#wp-link-cancel a' ).click( function( event ) {
 				event.preventDefault();
 				wpLink.close();
 			});