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

git-svn-id: https://develop.svn.wordpress.org/trunk@27510 602fd350-edb4-49c9-b593-d223f7449a82

src/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();
 			});