Lusca and HTTP parsing..

I've broken out most of the client-side request parsing code into a separate source file. There's now only a single entry and exit point (and one sideways jump for a comm timeout handler for now) from the client-side main code into the request handling code.

The main aim here is to eventually isolate and rework the whole process with which a HTTP request is parsed and constructed in memory. The process itself isn't all that CPU intensive these days compared to Squid-2.x and Squid-3.x but it is quite ugly. I won't go into the gory details - you can check it out for yourself if you like. Just cast your eyes over src/client_side_request_parser.c in LUSCA_HEAD.

I'm going to leave the request parsing code as it is for now. It's ugly but it works and its inefficiencies are dwarfed by the misuses of memory bandwidth/CPU cycles elsewhere.

I think I've left the codebase slightly easier to understand than before. I think I'm now at the point where I can document a large part of the client-side request and reply handling pipeline. The caching, vary and ETag processing is still very messy and too tightly integrated into the client-side code for my liking but as it also works fine for now I'll be leaving it well alone. There be dragons and all of that.