[Reviewer: Rob] Add support for protocol independent (IPv4/IPv6) table indices based upon RFC 4001.

I believe this is a way to move forward from the IpAddress table indices used in the current MIB. I'm not sure it is the best way. It is more of an experiment, and a place to start the discussion of how to proceed.
Comment to say what this is doing? (Having everything happening in the while loop condition, with no body, is not terribly clear - but I can live with it if there's a good comment.)