Allow orberby in wp_list_bookmarks to accept a comma-delimited list of fields, per docs. fixes #12421, props sorich87, scribu.

git-svn-id: http://svn.automattic.com/wordpress/trunk@14131 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-includes/bookmark.php

@@ -221,7 +221,10 @@ function get_bookmarks($args = '') {
 			$orderby = 'rand()';
 			break;
 		default:
-			$orderby = "link_" . $orderby;
+			$orderparams = array();
+			foreach ( explode(',', $orderby) as $ordparam )
+				$orderparams[] = 'link_' . trim($ordparam);
+			$orderby = implode(',', $orderparams);
 	}
 
 	if ( 'link_id' == $orderby )