Merge r5080: Add a new VCL variable "client.identity" which defaults to client.ip (without port number).

This variable is used by the "client" director to distribute sessions
across multiple backends.

Having it be a separate variable from client.ip makes it possible to
fill it from X-Forwarded-For: or Cookie headers.


git-svn-id: http://www.varnish-cache.org/svn/branches/2.1@5303 d4fa192b-c00b-0410-8231-f00ffab90ce4