To make the discussion more specific, here's a patch that adds support
for alternative newlines in _pyio.TextIOWrapper. It aslo updates the
documentation and adds more io tests. It does not provide C
implementation or the extended newline support for binary files.

As a side-effect it also fixes the bug in line_buffering=True
behavior, see issue22069O.

Note: The implementation does no newline translations unless in legacy
special cases i.e., newline='\0' behaves like newline='\n'. This is a 
key distinction from the behavior described in
http://bugs.python.org/file36008/pep-newline.txt

The initial specification is from
https://mail.python.org/pipermail/python-ideas/2014-July/028381.html