Bail out themes and plugins that have copied code from core and don't maintain it by requiring class-wp-editor.php in wp-langs.php, fixes #21350 for trunk

git-svn-id: https://develop.svn.wordpress.org/trunk@21345 602fd350-edb4-49c9-b593-d223f7449a82

wp-includes/js/tinymce/langs/wp-langs.php

@@ -3,6 +3,9 @@
 if ( ! defined( 'ABSPATH' ) )
 	exit;
 
+if ( ! class_exists( '_WP_Editors' ) )
+	require( ABSPATH . WPINC . '/class-wp-editor.php' );
+
 // deprecated, not used
 function mce_escape($text) {
 	return esc_js($text);