MEDIUM: http: Add a ruleset evaluated on all responses just before forwarding

This patch introduces the 'http-after-response' rules. These rules are evaluated
at the end of the response analysis, just before the data forwarding, on ALL
HTTP responses, the server ones but also all responses generated by
HAProxy. Thanks to this ruleset, it is now possible for instance to add some
headers to the responses generated by the stats applet. Following actions are
supported :

   * allow
   * add-header
   * del-header
   * replace-header
   * replace-value
   * set-header
   * set-status
   * set-var
   * strict-mode
   * unset-var
diff --git a/src/http_htx.c b/src/http_htx.c
index accfa19..587b9a5 100644
--- a/src/http_htx.c
+++ b/src/http_htx.c
@@ -1308,7 +1308,7 @@
 		if (htx_free_data_space(htx) < global.tune.maxrewrite) {
 			ha_warning("config: errorfile '%s' runs over the buffer space"
 				   " reserved to headers rewritting. It may lead to internal errors if "
-				   " http-final-response rules are evaluated on this message.\n",
+				   " http-after-response rules are evaluated on this message.\n",
 				   (char *)node->key);
 			err_code |= ERR_WARN;
 		}