RFR: jsr166 openjdk9 integration

[Martin Buchholz]

I added MOAT.java to the integration.

We noticed very rare failures testing WeakHashMap if the GC intervened at
just the wrong time.
(There's also changes to make the test portable to jdk8, since we still
test against that)

http://cr.openjdk.java.net/~martin/webrevs/openjdk9/jsr166-jdk9-integration/miscellaneous/test/java/util/Collection/MOAT.java.udiff.html