Provide code for common i-fix

[davemq]

Apparently there's a fairly common i-fix that's available, but the source code for it has not been available.

• [ ] Does this code already include that i-fix?
• [ ] If not, add the i-fix code to this code base

[davemq]

From Matt Glenn's e-mail about the i-fix and my reading of the code, the problem was in queryipf() and is already fixed.