test_fsync on MinGW(win32)

Hi.

I wanted to see this difference. It is somewhat ad hoc.
However, It is more effective than it doesn't show it at all.

-- MinGW(win32) --
$ test_fsync
Simple write timing:
        write                    3.644000

Compare fsync times on write() and non-write() descriptor:
(If the times are similar, fsync() can sync data written
 on a different descriptor.)
        write, fsync, close     40.543000
        write, close, fsync     47.033000

Compare one o_sync write to two:
        (o_sync unavailable)
        open o_dsync, write      0.094000

        (fdatasync unavailable)
        write, fsync,           26.700000

Compare file sync methods with 2 8k writes:
        open o_dsync, write      0.203000
        (fdatasync unavailable)
        write, fsync,           27.920000


Regards,
Hiroshi Saito