[PATCH] Support ICY protocol (ICECast / ICEShout servers) in Squid-3

Since we have no central place where the headers are upgraded I've had
to skip porting the upgrade_http0.9 hack in Squid-2 and go straight to
accepting ICY protocol as an accepted response protocol and handling it.

Somewhat primitive for now. It's limited to parsing and regenerating the
status line correctly, and skipping the HTTP/1.0 version override on
non-HTTP protocol replies.

Since it is on port 80 I've temporarily left the HTTP/1.1 required
header alterations happening. Some testing will be needed over the next
few days to ensure that the client software treats unknown headers
nicely. If needed overrides for those are easily done as well now.

Amos