Request for review - 8011268: NPG: Free unused VirtualSpaceNodes

[Jon Masamitsu]

After class unloading deallocate any VirtualSpaceNodes not being used.

When the classes for a dead class loader are unloaded, all the Metachunks
that had been used by that class loader are put on the Metachunk
free list for later reuse.   If all the Metachunks allocated out of a
VirtualSpaceNode are on the Metachunk free list, remove the Metachunks
  from the free list and deallocate the VirtualSpaceNode.

The constructor for VirtualSpaceNode was moved to be below the definition of
SpaceManager.

http://cr.openjdk.java.net/~jmasa/8011268/webrev.00/

Thanks.

Jon