Motivation:
In JDK9 the Cleaner.clean method cannot be called as it is not exported
from `java.base`. `Runnable.run` should be called instead.
Modifications:
Pick Runnable.run if the cleaner implements Runnable. Otherwise try the
clean method on the class implementing the cleaner.
Result:
The cleaner for direct byte buffers is run on JDK9 as well as earlier
JDKs.
cb071910ba