patch 8.1.0519: cannot save and restore the tag stack

Problem:    Cannot save and restore the tag stack.
Solution:   Add gettagstack() and settagstack(). (Yegappan Lakshmanan,
            closes #3604)
diff --git a/src/proto/list.pro b/src/proto/list.pro
index c4fd195..2f0b404 100644
--- a/src/proto/list.pro
+++ b/src/proto/list.pro
@@ -3,6 +3,7 @@
 void list_rem_watch(list_T *l, listwatch_T *lwrem);
 void list_fix_watch(list_T *l, listitem_T *item);
 list_T *list_alloc(void);
+list_T *list_alloc_id(alloc_id_T id);
 int rettv_list_alloc(typval_T *rettv);
 void rettv_list_set(typval_T *rettv, list_T *l);
 void list_unref(list_T *l);