[Accepted] SE-0029 Remove implicit tuple splat behavior from function applications

The review of "SE-0029 Remove implicit tuple splat behavior from function applications" ran from February 5...February 9, 2016. The proposal has been accepted for Swift 3. We acknowledge that we're removing a useful feature without providing an equally expressive drop-in replacement. However, maintaining this behavior in the type checker is a severe source of implementation complexity, and actively interferes with our plans to solidify the type system. We feel that removing the existing behavior is a necessary step toward stabilizing the language and toward building a well-designed alternative feature for explicit argument forwarding in the future. We will attempt to raise deprecation warnings for obvious cases in 2.2 (though the aforementioned technical debt makes warning comprehensively difficult).