[Nestmates] RFR: 8196320: [Nestmates] Restore the old enclosing-class based isSamePackageMember check in sun/invoke/util/VerifyAccess.java

[David Holmes]

Bug: https://bugs.openjdk.java.net/browse/JDK-8196320
webrev: http://cr.openjdk.java.net/~dholmes/8196320/webrev/

I've restored the original enclosing-class check and the 
isSamePackageMember method, but renamed it to areNestMates. It will 
first do the real Reflection.areNestMates check, and if that fails 
fall-back to the pre-nestmate enclosing class check.

I've added a test under runtime/Nestmates/legacy (where I'll accumulate 
tests that check legacy code still works after the nestmate changes - 
for specific areas like this.) The test will need tweaking once we bump 
the version to 11 (unfortunately there's no system property that reports 
the classfile version AFAICS).

Thanks,
David