Should open files in binary mode!

Also finally get rid of some obsolete commented-out access statements.

A note about the previous checkin: I believe it's correct, but I found
something strange: the file Lib/test/audiotest.au in the Python
distribution was evidently encoded in u-LAW format but had its
encoding set to 2, i.e. linear-8.  I hope that this is a mistake
caused by some conversion program that produced this .au file; I just
found it on a website.