Merge branch 'mainline' into lazy-args-in-futures

* mainline:
  Addition of test to verify fix for PMap's atPut()/dirty problem. Removal 
  of suboptimal fix for that problem from PMap, which is properly fixed by 
  Steve Dekorte's change to IoObject_setSlot marking an object dirty.
  Addition of test to verify fix for PMap's atPut()/dirty problem. Removal 
  of suboptimal fix for that problem from PMap, which is properly fixed by 
  Steve Dekorte's change to IoObject_setSlot marking an object dirty.
  New PDB test based on fix made to sync/atPut/sync workflow, plus inline 
  docs for many PDB methods.
  Workaround for sync/atPut/sync issue, force a PMap to re-persist after 
  atPut is called.
  Updated IoReference.html