BACKPORT: copy_value() doesn't preserve the identity relation

Imported from http://bugzilla.roxen.com/bugzilla/show_bug.cgi?id=3693

Reported by @grubba

From: PeterPan <peterpan@airinbox.com>
Resent-From: pike@roxen.com
To: "pike@roxen.com" <pike@roxen.com>
Date: Thu, 27 May 2004 10:05:45 +0800
Resent-Date: Thu, 27 May 2004 04:06:11 +0200 (MEST)
Subject: seems a bug

look this:
[peterpan@server01 ~/pikenv]$pike
Pike v7.6 release 6 running Hilfe v3.5 (Incremental Pike Frontend)
> array a1=({([])})*2;a1[0]==a1[1];
(1) Result: 0
> int t=2;array a2=({([])})*t;a2[0]==a2[1];
(2) Result: 1

the items in a1 are not same, but the items in a2 are same.