First "complete" implementation of to-be-closed variables

Still missing:
- handling of memory errors when creating upvalue (must run closing
method all the same)
- interaction with coroutines

testes/api.lua

@@ -1,4 +1,4 @@
--- $Id: testes/api.lua $
+-- $Id: testes/api.lua 2018-07-25 15:31:04 -0300 $
 -- See Copyright Notice in file all.lua
 
 if T==nil then
@@ -1027,6 +1027,18 @@ testamem("coroutine creation", function()
 end)
 
 
+-- testing to-be-closed variables
+testamem("to-be-closed variables", function()
+  local flag
+  do
+    local scoped x = function () flag = true end
+    flag = false
+    local x = {}
+  end
+  return flag
+end)
+
+
 -- testing threads
 
 -- get main thread from registry (at index LUA_RIDX_MAINTHREAD == 1)