Request for review (xs) - 8000325

[Jon Masamitsu]

This is a change in the default class unloading policy for CMS.

8000325:        Change default for CMSClassUnloadingEnabled to true

http://cr.openjdk.java.net/~jmasa/8000325/webrev.00/

With perm gen removal it becomes important for CMS to unload
classes to avoid excessive consumption of native memory for
metadata.