Implement basic infrastructure for upcoming GSLB experiments

[johanix]

This is mostly to document for the future, not the highest priority right now.

At the Vancouver IETF (120) we had a BOF on possibilities of achieving some sort of "standardization" of various (all proprietary) implementations of GSLB via DNS (GSLB=Global Server Load Balancing). The basic idea is to add some sort of new record to DNS that allows queries for a standard record (like an A) to receive dynamically computed responses based on external parameters (think "server load", originator location, current DB inventory levels, phase of the moon, etc).

I've seen suggestions for essentially encoding an SQL statement in the RDATA (hmmmm...) to slightly more sane suggestions that synthesize responses from data in an external K/V store.

What would be interesting to us is to be able to provide an open source implementation of something interesting to play with as a counterpoint to the various proprietary implementations that non-customers can only discuss theoretically. And as TDNS already has various DB connections this shouldn't be all that difficult for a first cut...