Sshd example on windows

I modified the samplesshd-cb example so it would build on Windows and added a bind option (which is copied over to become a session option) so the path to the moduli file can be optionally specified instead of defaulting to /etc/ssh/moduli. This gets the example running on Windows, although without libargp the example has to be tweaked to set that option.

These seemed small enough to put in the same merge request, but I can absolutely submit the new bind option separately if you'd prefer.

Checklist

• Commits have Signed-off-by: with name/author being identical to the commit author
• Code modified for feature
• Test suite updated with functionality tests
• Test suite updated with negative tests
• Documentation updated

Reviewer's checklist:

• Any issues marked for closing are addressed
• There is a test suite reasonably covering new functionality or modifications
• Function naming, parameters, return values, types, etc., are consistent and according to CONTRIBUTING.md
• This feature/change has adequate documentation added
• No obvious mistakes in the code