swift234

Handle "setter:" in @available(renamed:).

Example:

    @available(*, unavailable, renamed: "setter:CGRect.diagonal(self:_:)")
    func scale(_ rect: inout CGRect, toDiagonalLength length: CGFloat)

(My examples are getting more and more contrived, but there you go.)

This is pretty much the same as the getter handling, except that we also
want to strip off the '&' at the call site.