Issue #20510: Rewrote test_exit in test_sys to match existing comments
and to modernize.  Patch by Gareth Rees.
Issue #20609: Fix building 64-bit binaries on 32-bit Windows.
Issue #19612: On Windows, subprocess.Popen.communicate() now ignores
OSError(22, 'Invalid argument') when writing input data into stdin, whereas
the process already exited.