swift234

Unused binding analysis now recurses into type declarations

While we don't support classes that close over values in the outer
scope just yet, make the analysis handle it, to avoid emitting
spurious diagnostics about unused values.

For example, this would formerly daignose that 'x' was both unused
and that the closure was invalid:

func brigand() {
  let x = 0
  class Sword {
    func attack() {
      print(x)
    }
  }
}

Swift SVN r28480