Make test_zipfile pass.

The zipfile module now does all I/O in binary mode using bytes.
(Maybe we should support wrapping a TextIOWrapper around it
when text mode reading is requested?)
Even the password is a bytes array now.
Had to fix py_compile.py to use bytes while I was at it.
The _struct needed a patch to support bytes, str8 and str
for the 's' and 'p' formats.