* We should be able to use the ByteBuffer cleaner on java8 (and earlier versions) even if sun.misc.Unsafe is not present.
Motivation:
At the moment we have a hard dependency on sun.misc.Unsafe to use the Cleaner on Java8 and earlier. This is not really needed as we can still use pure reflection if sun.misc.Unsafe is not present.
Modifications:
Refactor Cleaner6 to fallback to pure reflection if sun.misc.Unsafe is not present on system.
Result:
More timely releasing of direct memory on Java8 and earlier when sun.misc.Unsafe is not present.
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