Various issues with callout-binding clone()

[stephan]

The following snippet causes various problems:

team class T {
   protected class R playedBy B {
       Object clone() => Object clone();
   }
}

• role method clone() is reported as not visible
• the generated callout method is wrongly marked as native
• base method clone() is OK for the compiler, but required decapsulation doesn't work at run-time

[stephan]

Bullets 1 & 2 are fixed in r17908 and r17909, resp. Test is in 3.1.3-otjld-concrete-callout-binding-5.

Bullet 3 is due to the inability to weave (decapsulate) system classes. It would be nice if the compiler could warn in these cases... Opened #64 for this remaining issue.