Attached is patch #3.  This one has been tested on Linux, Windows 7 64-bit, and Snow Leopard 64-bit.  Windows Server 2008 32-bit and 64-bit
are running now, looking good so far.

Changes:

* The order of arguments for OSError is now:
    (errno, string, filename, winerror, filename2)
  The winerror argument is always ignored on non-Windows platforms and
  may be any value.  Preserving the order of existing calls is
  important.  I considered making filename2 a keyword-only argument
  (as Georg suggested in IRC) but this would have made pickling and
  unpickling much more elaborate.

* Removed new functions taking Py_UNICODE at Serhiy's insistence.

* Removed PyErr_SetFromWindowsErrWithFilenameObject from documentation,
  as it doesn't even exist.

* Further documentation fixes.