'debug.[gs]etupvalue' should be able to access C upvalues too

ldblib.c

@@ -1,5 +1,5 @@
 /*
-** $Id: ldblib.c,v 1.110 2009/02/17 13:21:28 roberto Exp roberto $
+** $Id: ldblib.c,v 1.111 2009/08/04 18:27:57 roberto Exp roberto $
 ** Interface from Lua to its debug API
 ** See Copyright Notice in lua.h
 */
@@ -180,7 +180,6 @@ static int auxupvalue (lua_State *L, int get) {
   const char *name;
   int n = luaL_checkint(L, 2);
   luaL_checktype(L, 1, LUA_TFUNCTION);
-  if (lua_iscfunction(L, 1)) return 0;  /* cannot touch C upvalues from Lua */
   name = get ? lua_getupvalue(L, 1, n) : lua_setupvalue(L, 1, n);
   if (name == NULL) return 0;
   lua_pushstring(L, name);