(https://bugs.launchpad.net/zodb/+bug/400775)

Also, stop producing legacy PersistentMapping state, while still
accepting it.

tests have a clean transaction state and to avoid leaving files behind.

  all be accessed with those names in the modules (e.g.,
  BTrees.IOBTree.BTree).  This is in addition to the older names (e.g.,
  BTrees.IOBTree.IOBTree).  This allows easier drop-in replacement, which can
  especially be simplify code for packages that want to support both 32-bit and
  64-bit BTrees.

- Describe the interfaces for each module and actually declare the interfaces
  for each.

- Fix module references so klass.__module__ points to the Python wrapper
  module, not the C extension.

Most frequently "<unknown>" classes appears for objects changed
later in the same transaction with changes of an interesting objects
so we save data records for all objects changed in the transaction
and then check them for references.

automated test.  There were so many oddities getting that test
to pass, and so much consequent fiddling of other code, that I
don't intend to merge this to the 3.3 branch.  Also moved to
current Python CVS doctest.py, because the test really needs
the +ELLIPSIS option (tids vary across runs).