AudioStream: fix typo in notification name

darcs-hash:20090422072203-b2873-0f46cbbf39b454fc05486d0002eb2c407e62aa75
AudioStream.get_local_media: set default value for for_offer (True)

darcs-hash:20090422072229-b2873-b2402ca8b86e12815d150ead18d65e388b90f2cb