BUG/MINOR: http-rules: mention "deny_status" for "deny" in the error message

The error message indicating an unknown keyword on an http-request rule
doesn't mention the "deny_status" option which comes with the "deny" rule,
this is particularly confusing.

This can be backported to all versions supporting this option.
diff --git a/src/http_rules.c b/src/http_rules.c
index ab01f26..5089200 100644
--- a/src/http_rules.c
+++ b/src/http_rules.c
@@ -556,7 +556,8 @@
 		rule->cond = cond;
 	}
 	else if (*args[cur_arg]) {
-		ha_alert("parsing [%s:%d]: 'http-request %s' expects 'realm' for 'auth' or"
+		ha_alert("parsing [%s:%d]: 'http-request %s' expects 'realm' for 'auth',"
+			 " 'deny_status' for 'deny', or"
 			 " either 'if' or 'unless' followed by a condition but found '%s'.\n",
 			 file, linenum, args[0], args[cur_arg]);
 		goto out_err;