[Patch, Darwin, ObjC] default to sjlj exceptions only on m32.

[Mike Stump]

On Dec 17, 2010, at 2:11 AM, IainS <developer@sandoe-acoustics.co.uk> wrote:
> When we get m64 ObjC, we will be using unwind tables, therefore, don't set sjlj exceptions for m64.
> 
> OK for trunk?

Ok.