[Python-3000] New io system and binary data

[Skip Montanaro]

> P.S.:  If opening files on Linux is now to be semantically meaningful,
> then the documentation on that section also needs to change.  Currently
> it appears to mean that it's a meaningless specification that will be
> ignored unless you happen to be using the MSWindows platform.

I just checked in a change to the documentation for the builtin open function.
Please have a look at Doc/library/functions.rst and let me know if you
think more needs to be done.  Also, if there are other places in the
documentation
where it seems to imply that the distinction between text and binary modes is
meaningless on Unix systems, drop me a note and I'll have a look.

Skip