swift234

[sil-gen] Emit class methods for in protocol methods for classes so that
inherited conformances can result in virtual calls to overriding
subclass methods.

Previously given the following swift code:

  protocol P {
    func x()
  }
  class B : P {
    func x() { ... }
  }
  class B2 : B {
    func x() { ... }
  }
  func doX<T : P>(t : T) {
    t.x()
  }

  var b2 = B2()
  doX(b2)

We would have b2 reference the protocol method for B.x. But since the
protocol method B.x would have a direct function reference to B.x, we
would not get the correct behavior that doX(b2) should invoke B2.x. This
is fixed by changing SILGen to emit class_method calls in protocol
methods for classes.

Swift SVN r16645