#77183 (again) by m3avrck, add standard CSS to the maintenance pages.

includes/bootstrap.inc

@@ -712,5 +712,7 @@ function drupal_maintenance_theme() {
   require_once './includes/common.inc';
   require_once './includes/unicode.inc';
   unicode_check();
+  drupal_add_css(drupal_get_path('module', 'system') .'/defaults.css', 'core');
+  drupal_add_css(drupal_get_path('module', 'system') .'/system.css', 'core');
   $theme = '';
 }