RFR: JDK8 C2 fixes

[Roland Westrelin]

> - in inline_unsafe_access(), read-barriers should be moved up,
> otherwise we'd have one store in the else branch that does not have a
> read-barrier on its value.

Is this one required? The else branch stores outside the heap as I
understand.

> - for arraycopies, we must not turn oop-copies into int-copies, this
> would bypass the post-barrier that updates our references.

Ok.

Roland.