Checkpoint. Manipulated things so that string literals are always

Checkpoint.  Manipulated things so that string literals are always
unicode, and a few other compensating changes, e.g. str <- unicode,
chr <- unichr, and repr() of a unicode string no longer starts
with 'u'.  Lots of unit tests are broken, but some basic things
work, in particular distutils works so the extensions can be built,
and test_builtin.py works.