I tested this using a VM that lacks the exit code support, and found no problems.
All new VM builds will provide the primitive, so this belongs in trunk now.

On Sun, Oct 20, 2013 at 07:25:25PM +0000, commits at source.squeak.org wrote:
> David T. Lewis uploaded a new version of System to project The Trunk:
> http://source.squeak.org/trunk/System-ul.528.mcz
> 
> ==================== Summary ====================
> 
> Name: System-ul.528
> Author: ul
> Time: 12 May 2013, 10:33:50.489 pm
> UUID: d59743da-b5a5-4413-81f4-eb6dd7f7704d
> Ancestors: System-fbs.527
> 
> Added support for defining the exit code when quitting.
>