[tproxy] TPROXY4 and Squid-2/Cacheboy support

[Adrian Chadd]

G'day,

I've coded up some basic TPROXY4 support for my Squid-2 derivative,
Cacheboy. The HEAD version of Cacheboy should support both TPROXY2,
TPROXY4 and the FreeBSD-current tproxy-like functionality.

The TPROXY4 support will make it back into Squid-2 at some point.

I unfortunately don't have any local setup here to properly test the
TPROXY2 or TPROXY4 support; would someone on this list be able to give
me a hand in verifying that the code does as advertised?

(The TPROXY2 code is based on the TPROXY2 support from Squid-2.HEAD,
but I've tried modularising it somewhat so it can be easily replaced
by other transproxy implementations, such as the FreeBSD and OpenBSD
variants. This is why I'd also like some help testing the legacy code.
:)

Thanks!


Adrian