ab85ff3 fixed for 3.2.2 problems with
subprocess and universal_newlines=True, notably the use of select() on its
output.  The problem can be seen its parent commit
e96ec68, and seems to come from a big
py3k refactoring.  This particular issue is exercised by new
test_stdout_pipe_readline_select().

However, it still does not work with poll(), as shown by new
test_stdout_pipe_readline_poll(), issue recorded in
https://bugs.python.org/issue41222

Both tests pass on 2.7 (once adapted to use raw_input() rather than getting
py3 input() semantics).

Note: a related problem was solved 877766d
for 3.1.4 for universal_newlines=False.  The testcase provided in that
commit also does not check that select() will work after not all data
was read.

Signed-off-by: Yann Dirson <ydirson@free.fr>