core: allow route(...) usage inside onsend_route block

- GH #4130

src/core/cfg.y

@@ -2914,6 +2914,7 @@ fcmd:
 				case MODULE5_T:
 				case MODULE6_T:
 				case MODULEX_T:
+				case ROUTE_T:
 				case SET_FWD_NO_CONNECT_T:
 				case SET_RPL_NO_CONNECT_T:
 				case SET_FWD_CLOSE_T: