[Coco] gcc6809 bug

[James Dessart]

This bug was fixed on my end for a while, but I just got around to 
committing it to CVS in the gcc-coco project at sourceforge. The bug 
would occur when subtracting a register from a constant, for example:

x = 1 - x;

The compiler with the bug would generate an internal compiler error for 
this case. The fix is to m6809.md, in CVS. If you use gcc6809, I would 
recommend updating your source files from CVS and rebuilding.

In the mean time, I'm going to work on getting a Mac OS X binary up on 
sourceforge. If someone would be so kind as to provide a build based on 
the latest sources for linux-x86 and cygwin, that'd be great!

James