1. That seeking beyond the end of a file increases the size of a file.
2. That files so extended are magically filled with null bytes.
I find no support for either in the C std, and #2 in particular turns out
not to be true on Win32 (you apparently see whatever trash happened to be
on disk). Left #1 intact, but changed the test to check only bytes it
explicitly wrote. Also fiddled the "expected" vs "got" failure reports
to consistently use repr (%r) -- they weren't readable otherwise.
Curious: the MS docs say stati64 etc are supported even on Win95, but
Win95 doesn't support a filesystem that allows partitions > 2 Gb.
test_largefile: This was opening its test file in text mode. I have no
idea how that worked under Win64, but it sure needs binary mode on Win98.
BTW, on Win98 test_largefile runs quickly (under a second).
catch IOError as well as OverflowError. I found that on Tru64 Unix
this was raised; probably because the OS (or libc) doesn't support
large files but the architecture is 64 bits!