RFR 8055098: WB API should be extended to provide information about size and age of object.

[Leonid Mesnik]

Dear All

Could I have review for this patch.
issue: https://bugs.openjdk.java.net/browse/JDK-8055098
webrev: http://cr.openjdk.java.net/~jcoomes/8u/lmesnik/8055098-wbapi/
This patch applied clearly to jdk8u and jdk9. This is RFR for 
integration into jdk9/hs-gc. The RFR for backporting I'll send after fix 
is integrated into jdk9.

Fix:
WB API was extended by methods which allow to know object size and if it 
is in old generation. Also whitebox method which added young GC was 
added. Fix included unit test.
Testing: JPRT for 8u and 9, adhoc testing with different GCs.

Thank you
Leonid