[swift-evolution] Add conversion String -> Bool

[Chris Lattner]

> On Jun 4, 2016, at 7:22 AM, Brent Royal-Gordon via swift-evolution <swift-evolution at swift.org> wrote:
> 
>> It would be great if we had `init?(_ text: String)` for Bool class. Because sometime when you're processing JSON/XML it can help you a lot.
> 
> Way ahead of you: https://github.com/apple/swift-evolution/blob/master/proposals/0089-rename-string-reflection-init.md
> 
> (I'm not quite sure what's going on with the "scheduled for review" at the top, so let's leave that bit aside for now.)

Too much going on right now, and I lost track of this. I’ll kick off the review.

-Chris