Ridiculously, this `struct` was defined in the Windows 2000 SDK and promptly dropped.  I guess this was done with the addition of the `CreateSymbolicLink` and `CreateHardLink` APIs, because this API suuuuuuuuuuuucks.  But that's just a hunch, and whatever the reason, it means we have to include it ourselves.  This was copied from MSDN.