RFR (L): 8022853: add ability to Unsafe to load and store uncompressed object and Klass references in a compressed environment

[Christian Thalinger]

http://cr.openjdk.java.net/~twisti/8022853/webrev/
http://cr.openjdk.java.net/~twisti/8022853-jdk/webrev/

8022853: add ability to Unsafe to load and store uncompressed object and Klass references in a compressed environment
Reviewed-by:

In some native data structures of the VM oops are stored uncompressed when compressed oops are turned on, for example Klass::_java_mirror. Java code which is tightly coupled with the VM should have the ability to read and write such fields.