Added a counter of the total number of existing objects

It may simplify the control of the garbage collector.

lstate.c

@@ -279,6 +279,7 @@ static void close_state (lua_State *L) {
   luaM_freearray(L, G(L)->strt.hash, G(L)->strt.size);
   freestack(L);
   lua_assert(gettotalbytes(g) == sizeof(LG));
+  lua_assert(g->totalobjs == 1);
   (*g->frealloc)(g->ud, fromstate(L), sizeof(LG), 0);  /* free main block */
 }
 
@@ -387,6 +388,7 @@ LUA_API lua_State *lua_newstate (lua_Alloc f, void *ud) {
   g->weak = g->ephemeron = g->allweak = NULL;
   g->twups = NULL;
   g->totalbytes = sizeof(LG);
+  g->totalobjs = 1;
   g->GCdebt = 0;
   g->lastatomic = 0;
   setivalue(&g->nilvalue, 0);  /* to signal that state is not yet built */