[MINOR] config: some options were missing for "redirect"

Those options were missing in the parser error message :
  set-cookie, clear-cookie, drop-query
diff --git a/src/cfgparse.c b/src/cfgparse.c
index fdaa606..938caf1 100644
--- a/src/cfgparse.c
+++ b/src/cfgparse.c
@@ -1844,7 +1844,7 @@
 				break;
 			}
 			else {
-				Alert("parsing [%s:%d] : '%s' expects 'code', 'prefix' or 'location' (was '%s').\n",
+				Alert("parsing [%s:%d] : '%s' expects 'code', 'prefix', 'location', 'set-cookie', 'clear-cookie' or 'drop-query' (was '%s').\n",
 				      file, linenum, args[0], args[cur_arg]);
 				err_code |= ERR_ALERT | ERR_FATAL;
 				goto out;