swift234

[IDE/CodeCompletion] Teach code completion to display the local parameter name
if there's no parameter API name. This is for display purposes only.
Update all relevant tests accordingly.
This addresses <rdar://problem/16768768>.

For example:
  class X {
    func f(a: Int, b: Int) { }
  }

Would previously display like this in code completion in Xcode:
  f(<#Int#>, b: <#Int#>)

The local parameter name, while not API, often still conveys meaning
to the user. So it's now included like this:
  f(<#a: Int#>, b: <#Int#>)

Swift SVN r18403