[3.0.0] [BACKPORT]

- Add register() for DefinitionCacheFactory so custom implementations can be specified
- Add docs for flush() regarding when this functionality is impossible to do
- Refactor unit tests in DefinitionCacheFactoryTest.php

git-svn-id: http://htmlpurifier.org/svnroot/htmlpurifier/trunk@1464 48356398-32a2-884e-a903-53898d9a118a

library/HTMLPurifier/DefinitionCache.php

@@ -104,6 +104,9 @@ abstract 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.
      */
     abstract public function cleanup($config);