PR pkg/39188.
New feature with Squid 3.0.
* Code converted to C++, with significant internal restructuring and rewrites.
* ICAP implementation (RFC 3507 and www.icap-forum.org)
* Edge Side Includes (ESI) implementation (www.esi.org)
Missing feature from squid 2.6
* refresh_stale_hit option. Not yet ported.
* ability to follow X-Forwarded-For. Not yet ported.
* Full caching of Vary/ETag using If-None-Match. Only basic Vary cache
supported. Not yet ported.
* Mapping of server error messages. Not yet ported.
* http_access2 access directive. Not yet ported.
* Location header rewrites. Not yet ported.
* wais_relay. Feature dropped as it's equivalent to cache_peer +
cache_peer_access.
* urlgroup. Not yet ported.
* collapsed forwarding. Not yet ported.
* stable Windows support. Irregularly maintained.
Currently, COSS backend support isn't available, too.
