MPR#7385: fix Unix.stat timestamps during DST
MPR#7385: fix Unix.stat timestamps during DST

The Win32 API used treats DST as a timezone offset rather than a bias,
resulting in all timestamps being an hour out when the system date is
during DST.

gerdstolpmann/ocaml,gerdstolpmann/ocaml,gerdstolpmann/ocaml,gerdstolpmann/ocaml,gerdstolpmann/ocaml