RFR: 8198528: Move GenerationSpecs from GenCollectorPolicy to GenCollectedHeap

[Stefan Karlsson]

Hi all,

Please review this patch to move _young_gen_spec and _old_gen_spec out 
from GenCollectorPolicy into GenCollectedHeap.

  http://cr.openjdk.java.net/~stefank/8198528/webrev.01/
  https://bugs.openjdk.java.net/browse/JDK-8198528

This is a step towards the removal of CollectorPolicy:

  https://bugs.openjdk.java.net/browse/JDK-8198505

Thanks,
StefanK