[RFA] Darwin: single step through sigreturn

[Mark Kettenis]

> From: Tristan Gingold <gingold@adacore.com>
> Date: Thu, 4 Dec 2008 16:28:25 +0100
> 
> Hi,
> 
> as other platform, single stepping through the sigreturn syscall is  
> special: changing the cpu state
> is useless as the context is restored.  The trace bit must be set in  
> the to be restored context.

Tristan,

It seems your mail client munges diffs (by wrapping lines).  Otherwise
it looks ok.

Mark