TPROXY support

G'day,

I've done a bit of shuffling in the communication code to include a more modular approach to IP source address spoofing.

There's (currently) untested support for some FreeBSD source IP address spoofing that I'm bringing over courtesy of Julian Elischer; and there's a Linux TPROXY2 module.

I'll look at porting over the TPROXY4 support from Squid-3 in a few days.

I think this release is about as close to "stable" as Cacheboy-1.6 is going to get, so look forward to a "stable" release as soon as the FreeBSD port has been setup.

I already have a list of things to do for Cacheboy-1.7 which should prove to be interesting. Stay tuned..