[8u] Request for Approval: 8185572: Enable AssumeMP by default on SPARC machines

[Poonam Parhar]

Please approve the request to backport the fix for 8185572 to jdk8u.

These changes enable the JVM option AssumeMP by default on Sparc systems. The changes apply cleanly to 8u-dev.
Bug: https://bugs.openjdk.java.net/browse/JDK-8185572
Review thread: http://mail.openjdk.java.net/pipermail/hotspot-compiler-dev/2017-August/026819.html
JDK 10 Changeset: http://hg.openjdk.java.net/jdk10/hs/hotspot/rev/ca50acf57289

Thanks,
Poonam