Patch: A few small features for Squid 2.5

While using Squid as an httpd-accelerator and general front-end server
for SSL handling and distributing requests, I added a few small features
that I needed. I am sending this patch to the list in case anybody else
is interested in these humble improvements.

The added options are:
- peer option 'httpd' sends normal HTTP requests to that peer instead of
  proxy requests.
- peer option 'immortal' prevents the peer from ever being marked dead.
- global option 'forward_retries' allows the previously hardcoded number
  of retries (10) to be changed.
- global option 'httpd_accel_with_icp' turns on ICP without turning on
  full proxy mode.

Regards, Karsten

P.S. Please CC any replies to me, as I am not subscribed to the list.