swift234

[ClangImporter] Skip setters in protocols if there's a readonly property.

This is a workaround for us saying that the setter generated for a property
conflicts with the setter-method explicitly declared in the Objective-C
protocol. (After all, they do have the same name.) If we really want to
support this, we need something like "var foo { get optional set }", which
our model doesn't really support right now. But we should at least allow
the user's code to build.

rdar://problem/19933285

Swift SVN r25634