Fixing the type system

[xwu (Xiaodi Wu)]

See the following thread, and related threads:

Splat

So, since SE-0029 has been accepted, let's think about explicit replacements. So far, I've been able to think of three general approaches. For the examples below, I'll assume there's a `func concatenate(number: Int, to string: String) -> String`, which does the obvious thing. Where supported, I will fully qualify names with SE-0021 syntax, but in some cases this might not be necessary.     1. Special parameter label. `concatenate` is implicitly overloaded with a `func concatenate(parameters: (…