Change how class tables are created and recreated for greater robustness

luprex/cpp/core/luastack.hpp

@@ -458,9 +458,11 @@ public:
     void makeclass(LuaSlot tab, std::string_view name) const;
 
     // Create a tangible, or look up an existing tangible.
-    // This doesn't do the entire process of tangible creation.  It
-    // just creates an empty table, marks it as a tangible, creates
-    // the metatable, stores the tangible ID, and stores it in the tangible table.
+    // If the tangible doesn't exist yet, this creates a tangible stub.
+    // It is possible to use World::tangible_make to transform a tangible
+    // stub into a full blown tangible, and World::tangible_delete to turn
+    // a full-blown tangible back into a stub.  A stub doesn't have a
+    // class or a thread table.
     void maketan(LuaSlot tab, int64_t id) const;
 
     // Return true if a tangible is empty (deleted or not yet created).