Quickfix "add unimplemented methods" not working for roles

[stephan]

The quickfix for adding unimplemented methods does not work for implicitly inherited abstract methods.

Reported by Ralf Müller.

[stephan]

Test and fix are in r18836.

The error message had suggested a compile error, but the actual problem was only that no implementable methods were found.

As a related bug the following produced an error saying that T3.R must implement foo:

public team class T1 {
    public abstract class R {
        abstract void foo();
    }
}
public team class T2 {
    public class R  playedBy B {
        void foo() -> void bar();
    }
}
public team class T3 {
    public class R { }
}

This was actually fixed in r18782 (callout method was not created for type T2.R which was not the focus type). See test in r18837.