(Yes, I've been slack in posting about this stuff.)
I'm just about to roll the next Cacheboy-1.5 development pre-release. Cacheboy-1.5 is probably the last "almost but not quite squid-2.HEAD" release. Besides the IPv6 core, Cacheboy-1.5 resembles the Squid code but with a more sensible layout of modules and libraries.
Its main difference is the inclusion of core comm layer changes to support IPv6 in preparation of IPv6 client and server support. This particular pre-release includes some changes to the internal DNS code to decouple it from a few routines in src/ relating to TCP socket connection. Its possible I've busted stuff - just run cacheboy with "debug_options ALL,1 78,2" for a while to see if you're falling back to TCP DNS properly.
I'm about to put Cacheboy-1.5.PRE3 in production for a couple of clients to get some real world feedback.