namei: Abstract out OGM functions a bit more

Add GetWinOGM and SetWinOGM for getting and setting the
Windows-equivalent of the Unix OGM data. Make those and CheckOGM use
GetFileTime/SetFileTime so we can operate just via an FD_t, without
needing the full pathname. Modify the NT namei_icreate to use
SetWinOGM.

Reviewed-on: http://gerrit.openafs.org/6945
Reviewed-by: Jeffrey Altman <jaltman@secure-endpoints.com>
Reviewed-by: Derrick Brashear <shadow@dementix.org>
Tested-by: Derrick Brashear <shadow@dementix.org>
(cherry picked from commit 0594fc80b48152b4b03edda7e19133b59fc0670e)

Change-Id: I65491a9a82911d9c99d6238a4ea66ed400db7aa0
Reviewed-on: http://gerrit.openafs.org/9281
Reviewed-by: Derrick Brashear <shadow@your-file-system.com>
Reviewed-by: Andrew Deason <adeason@sinenomine.net>
Reviewed-by: Mark Vitale <mvitale@sinenomine.net>
Reviewed-by: Stephan Wiesand <stephan.wiesand@desy.de>
Tested-by: BuildBot <buildbot@rampaginggeek.com>