1) in all module-indpendent code the variable $quiz has been renamed to $cmoptions (it holds the options set by the course module which does not necessarily have to be a quiz, it could be a lesson for example).
2) quiz_restore_question_sessions() has the simpler name quiz_get_states
Also got rid of the quizfile.php in favour of file.php
Moved all code that is not specific to the quiz module out of locallib.php into questionlib.php.
The default questiontype class is now defined in quiz/questiontypes/questiontype.php.
See http://mantis.york.ac.uk/moodle/mod/forum/discuss.php?d=852