[swift-evolution] Update the signature of ObjectiveC.autoreleasepool [SR-842]

[Chris Lattner]

> On Mar 29, 2016, at 4:18 PM, Dave Abrahams via swift-evolution <swift-evolution at swift.org> wrote:
> 
> 
> on Tue Mar 29 2016, Joe Groff <swift-evolution at swift.org> wrote:
> 
>> Yeah, I agree with Jordan, the analogy to `forEach` makes no sense,
>> Chris. The standard library is overwhelmingly consistent in forwarding
>> return values from its "scope-guard"-like functions which set up a
>> thing, call a closure once, clean up the thing, then
>> return. `autoreleasepool` is the odd one out.
> 
> +1; there's really no good reason to hobble autoreleasepool AFAICS.

Ok, it sounds like there is support for the return value.  Tim, feel free to include it, but mention that it is controversial in the “alternatives considered” section.  The community can hash it out in the review period, thanks!

-Chris