Bug: 'local function' can assign to '<const>' variables

lparser.c

@@ -1785,6 +1785,7 @@ static void funcstat (LexState *ls, int line) {
   luaX_next(ls);  /* skip FUNCTION */
   ismethod = funcname(ls, &v);
   body(ls, &b, ismethod, line);
+  check_readonly(ls, &v);
   luaK_storevar(ls->fs, &v, &b);
   luaK_fixline(ls->fs, line);  /* definition "happens" in the first line */
 }