Replace obj "reachable" with flags

src/memory.c

@@ -83,6 +83,7 @@ struct ucl_object *ucl_special_create(struct ucl* ucl, ucl_lisp special)
 static struct ucl_object* ucl_object_alloc(struct ucl* ucl) {
     struct ucl_object *obj =  ucl_arena_get(ucl->obj_arena);
     assert(obj != NULL);
+    obj->flags = 0;
     return obj;
 }
 
@@ -123,11 +124,11 @@ void ucl_object_delete(struct ucl* state, struct ucl_object *obj) {
 }
 
 static void ucl_object_mark(struct ucl_object *obj) {
-    if (obj == NULL || obj->reachable) {
+    if (obj == NULL || obj->flags & UCL_OBJ_FLAG_REACHABLE) {
         return;
     }
 
-    obj->reachable = 1;
+    obj->flags |= 1;
     if (obj->type == UCL_TYPE_CELL) {
         ucl_object_mark(obj->cell.car);
         ucl_object_mark(obj->cell.cdr);
@@ -144,13 +145,13 @@ static void ucl_scope_mark(struct ucl_arena * arena, void *obj) {
 static void ucl_gc_unmark(struct ucl_arena * arena, void *obj) {
     (void) arena;
     struct ucl_object *object = (struct ucl_object *) obj;
-    object->reachable = 0;
+    object->flags &= ~UCL_OBJ_FLAG_REACHABLE;
 }
 
 static void ucl_gc_sweep(struct ucl_arena * arena, void *obj) {
     (void) arena;
     struct ucl_object *object = (struct ucl_object *) obj;
-    if (object->reachable == 0) {
+    if (!(object->flags &UCL_OBJ_FLAG_REACHABLE)) {
          ucl_object_delete_internal(arena, object);
     }
 }

src/types.h

@@ -40,7 +40,7 @@ struct ucl_object {
         ucl_lisp special;
     };
     enum ucl_type type;
-    char reachable;
+    char flags;
 };
 
 struct ucl_scope {