Here's a preliminary implementation of the PEP,
including unittests  checking the promises made in the
PEP (test_bool.py) and (some) documentation.

With this 12 tests fail for me (on Linux); I'll look
into these later.  They appear shallow (mostly doctests
dying on True or False where 1 or 0 was expected).

Note: the presence of this patch does not mean that the
PEP is accepted -- it just means that a sample
implementation exists in case someone wants to explore
the effects of the PEP on their code.