RFR(XS): 8246689: Enable independent compressed oops/class ptrs on Aarch64

[Patric Hedlin]

Dear all,

I would like to ask for help to review the following change/update:

Issue:  https://bugs.openjdk.java.net/browse/JDK-8246689
Webrev: http://cr.openjdk.java.net/~phedlin/tr8246689/


Aarch64 was not included in JDK-8241825. This small patch enables the 
feature on Aarch64 and updates the associated test-case (in tier2). This 
patch is an attempt to make tier2 all green for linux-aarch64, that we 
want to run in regular testing (see JDK-8246691).

Testing: tier1-2 and a number of runs of RunThese30M.


Best regards,
Patric