Partial fix for some EXCESS cdMark computed inter-handle reference counts
Partial fix for some EXCESS cdMark computed inter-handle reference counts

This commit partially fixes one cause of EXCESS cdMark computed inter-handle reference
counts.  Specifically, 'cdMark' will increment the inter-handle reference count of any
handle it has a reason to visit.  Once the garbage collector consumes those counts, it
must reset (_VContainerHandle::unmark ()_) them for the benefit of subsequent garbage
collections.  Because any handle can be 'cdMark'ed, every handle must be 'unmark'ed.
As currently implemented, 'EnqueueOmittingCycles' has responsibility for consuming and
reseting those counts.  A bug in its logic, fixed here, had it 'unmark'ing only those
handles it had a reason to enqueue for preservation.  As expected, in sessions that
ran multiple garbage collections ('Utility collectGarbage; Utility updateNetwork'),
EXCESS counts were occuring.

Note that this is only a partial fix and does not address a deeper problem involving
transient (session) garbage collections.  Because the transient garbage collector only
examines modified spaces, the potential remains for un-reset inter-handle reference
counts in the un-modified spaces that 'EnqueueOmittingCycles' will never be asked to
process.

vision-dbms/vision,vision-dbms/vision,VisionAerie/vision,c-kuhlman/vision,VisionAerie/vision,c-kuhlman/vision,vision-dbms/vision,c-kuhlman/vision,vision-dbms/vision,MichaelJCaruso/vision,VisionAerie/vision,MichaelJCaruso/vision,MichaelJCaruso/vision,MichaelJCaruso/vision,VisionAerie/vision,vision-dbms/vision,MichaelJCaruso/vision,vision-dbms/vision,VisionAerie/vision,c-kuhlman/vision,MichaelJCaruso/vision,c-kuhlman/vision,VisionAerie/vision,VisionAerie/vision