Enable large file support on Win32 systems.
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).
5 files changed