consolidate plugin/theme/core upgrade/install functions. Props DD32. see #7875

git-svn-id: http://svn.automattic.com/wordpress/trunk@11005 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-admin/includes/update-core.php

@@ -229,7 +229,7 @@ function update_core($from, $to) {
 	$result = copy_dir($from . '/wordpress', $to);
 	if ( is_wp_error($result) ) {
 		$wp_filesystem->delete($maintenance_file);
-		//$wp_filesystem->delete($working_dir, true); //TODO: Uncomment? This DOES mean that the new files are available in the upgrade folder if it fails.
+		$wp_filesystem->delete($working_dir, true);
 		return $result;
 	}