[Coco] NitrOS9 and 6309 code

[Allen Huffman]

> On May 31, 2019, at 9:24 PM, L. Curtis Boyle <curtisboyle at sasktel.net> wrote:
> 
> I think we should make a unique error code that explicitly states that a 6309 module can not run on a 6809 system. We have a fair number of open spaces in the error codes to put such an error code in. “Bad module header” can mean corrupt modules, etc. as well, so I would prefer to differentiate it.

Let me confirm if there’s already an error code used by OS-9(000) for this purpose, and we can mirror that.

		— A