Message 232828 - Python tracker

Suggestions from Antoine on python-dev:

* do not make cOrderedDict "builtin"; drop changes to:
  - Include/Python.h
  - Objects/object.c
  - Makefile.pre.in
* do not add a C-API
* include the linked list pointers in the hash entries? (may simplify things)
* drop the shared/split keys mechanism?
* do not subclass dict? (can of worms)