Minor: comment about Libraries 7.x-2.x.

apps/class_grapher/classgrapher.drush.inc

@@ -84,6 +84,8 @@ function _drush_classgrapher_get_formats() {
  * Validation callback for classgraph.
  */
 function drush_classgrapher_classgraph_validate() {
+  // Libraries 7.x-1.x does not include this function, and Drush
+  // 'drupal dependencies' can not require a specific branch.
   if (function_exists('libraries_load')) {
     $info = libraries_load('grammar_parser');
   }