RFR: 8205340: [lworld] Re-enable _hashCode, _identityHashCode and _newArray intrinsics

[Roland Westrelin]

http://cr.openjdk.java.net/~roland/8205340/webrev.00/

I expect this change to fix all remaining intrinsics. I found that
flattened array allocation through reflection would never go through the
fast path. Once that was fixed then I hit some failure in
arraycopy/copyOf tests that this patch fixes. hashCode() tests are
currently commented out because they trigger the bug I reported on this
list earlier:

http://mail.openjdk.java.net/pipermail/valhalla-dev/2018-June/004383.html

The tests did pass when I developped this patch on an older revision of
the repo.

Roland.