[ofw] Porting OFA stack to WDK

[Sean Hefty]

>The size of structures would change, so yes, apps would need to recompile.  You
>could add #ifdef'd padding to keep the 32-bit structures the same size and
>preserve binary compatibility.

So, adding padding would preserve binary compatibility for structures, but not
the interfaces, and if an app did recompile it would likely require minor code
changes to remove any casts that it has in place.  (Do we have an idea of how
many window apps there are outside of the OFA tree?)

Is keeping the userspace interfaces the same, but changing the kernel interfaces
to remove __ptr64 a usable solution?

- Sean