backport 1.18, 1.19, 1.20:
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Apply two small changes to the Windows code, according to SF bug
#427345.  These are supposed to support binary data and avoid
buffering problems on Windows.
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SF patch #467430.
- replace some log_error() calls with log_message()
- flush self.rfile before forking too (hope this works on Windows)
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Fix two typos, one noted by Noah Spurrier in SF bug #475166, the
second noted after a second's thought about what the next line should
do. :-(