[ofw] winverbs ND provider

[Sean Hefty]

I've submitted a set of 4 patches against the stack to address performance
differences between the ibal and winverbs providers.  (One of the patches is to
fix a bug that I hit while working on the other patches.)

Based on ndconn results, the winverbs ND connection rate is still less than that
reported for the ibal ND provider.  I'm not sure how much emphasis we should
place on the ndconn rates, however, or connection rates at all for that matter.
The main difference between the providers is that winverbs uses multiple threads
to process connections asynchronously.  It's possible that this actually lowers
ndconn numbers, but it would take more extensive testing to confirm this.

The winverbs ND provider was also updated to use inline data.  In my testing,
this gave similar latency numbers as the ibal ND provider.

If anyone is aware of other performance differences between the two providers,
please let me know as soon as possible.  I will continue to stress the code for
the next couple of days before committing the changes to the trunk.

- Sean