[ofw] more info on kernel winverbs interface

[Sean Hefty]

The idea of having a winverbs kernel interface was brought up at the last WWG
call.  I just wanted to get more information on the request.

Which interfaces are people wanting, and what OS versions would this need to be
available on?  The latter is a concern for the CM related interfaces, as I
believe the needed kernel level networking APIs only exist starting with 2008.
(Although I guess it's possible for the kernel to communicate with some
userspace service that can provide it the necessary details.)