[3.1.0] Improve maintenance script documentation

git-svn-id: http://htmlpurifier.org/svnroot/htmlpurifier/trunk@1644 48356398-32a2-884e-a903-53898d9a118a

maintenance/generate-includes.php

@@ -10,6 +10,8 @@ assertCli();
 /**
  * @file
  * Generates an include stub for users who do not want to use the autoloader.
+ * When new files are added to HTML Purifier's main codebase, this file should
+ * be called.
  */
 
 chdir(dirname(__FILE__) . '/../library/');