add hit, miss, grace, keep, and ttl headers

hit_miss.vcl

vcl 4.0;

#put this near the top of the parent vcl:
#include "hit_miss.vcl";

sub vcl_hit
{
  set req.http.X-status = "HIT";
  set req.http.X-ttl = obj.ttl;
  set req.http.X-grace = obj.grace;
  set req.http.X-keep = obj.keep;
}

sub vcl_miss
{
  set req.http.X-status = "MISS";
}

sub vcl_pass
{
  set req.http.X-status = "PASS";
}

sub vcl_backend_response
{
  set beresp.http.X-full-ttl = beresp.ttl;
}

sub vcl_deliver
{
  set resp.http.X-status = req.http.X-status;
  set resp.http.X-hits = obj.hits;
  if (resp.http.X-status == "HIT")
  {
    set resp.http.X-ttl = req.http.X-ttl;
    set resp.http.X-grace = req.http.X-grace;
    set resp.http.X-keep = req.http.X-keep;
  }
}