Reverting IPv6 for now; moving forward with structural changes

I've been working on the IPv6 support in Cacheboy for a couple months now and I've come to the conclusion that I'm not getting anywhere near as far along the development path as I wanted to be.

So I've taken a rather drastic step - I've branched off CACHEBOY_HEAD from the last point along the main codebase where the non-intrusive IPv6 changes had occured and I'm going to pursue Cacheboy-1.6 development from that.

The primary short-term goal with Cacheboy was to restructure the codebase in such a way as to make further development much, much simpler. I sort of lost track with the IPv6 development stuff and I rushed it in when the codebase obviously wasn't ready.

So, the IPv6 changes will stay in the CACHEBOY_PRE branch for now; development will continue in CACHEBOY_HEAD. I'll continue the restructuring work and stability work towards a Cacheboy-1.6 release come January 1. I'll then look at merging over the IPv6 infrastructure work into CACHEBOY_HEAD far before I merge in the client and server related code - specifically, completing the DNS updates, the ipcache/fqdncache updates, port over the IPv6 SNMP changes from Squid-3, and look at modularising the ACL code in preparation for IPv6'ifying that. The goal is less to IPv6-ify Cacheboy; its more to tidy up the code to the point where IPv6 becomes trivial.