RFR (XS): 8149611: Add tests for Unsafe.copySwapMemory

[Mikael Vidstedt]

When I prepared the change for JDK-8141491 [1] I accidentally forgot to 
hg add the new jtreg tests for the new Unsafe.copySwapMemory method. 
This change adds the tests:

Bug: https://bugs.openjdk.java.net/browse/JDK-8149611
Webrev: http://cr.openjdk.java.net/~mikael/webrevs/8149611/webrev.00/

Cheers,
Mikael

[1] https://bugs.openjdk.java.net/browse/JDK-8141491