[swift-evolution] Make non-void functions @warn_unused_result by default

[Chris Lattner]

> On Feb 24, 2016, at 7:13 AM, Janosch Hildebrand via swift-evolution <swift-evolution at swift.org> wrote:
> 
> Erica's proposal about "Modernizing Attribute Case and Attribute Argument Naming" made me remember this discussion.
> 
> I don't think a proposal was ever submitted? If no one else is working on a proposal already I would offer myself up for writing this up.

I don’t recall a real proposal, it would be great for you to drive this.

-Chris