[2.1.4] [MFH] register() for DefinitionCacheFactory from r1464

git-svn-id: http://htmlpurifier.org/svnroot/htmlpurifier/branches/php4@1711 48356398-32a2-884e-a903-53898d9a118a

library/HTMLPurifier/DefinitionCache.php

@@ -120,6 +120,9 @@ class HTMLPurifier_DefinitionCache
     
     /**
      * Clears all expired (older version or revision) objects from cache
+     * @note Be carefuly implementing this method as flush. Flush must
+     *       not interfere with other Definition types, and cleanup()
+     *       should not be repeatedly called by userland code.
      */
     function cleanup($config) {
         trigger_error('Cannot call abstract method', E_USER_ERROR);