Rewrite new_persistent_id() to make it clear what's going on.
Jeremy Hylton authored
Reformat all the code to use Python style.

We got an undiagnosed bug report for coptimization, which lead to an
attempt at code review.

Break up a the large new_persistent_id() function into several helpers
-- get_class(), get_class_tuple(), and set_oid().  Each function now
does a little less.  Don't reuse variable names for random purposes.
e94f7e66