Correctly add the QueueID to a pending block's extended thread backtrace thread.

Seed the QueueItem objects with the item_refs and addresses when they are fetched
in one batch.  If additional information is needed from the QueueItem, fetch it
lazily one pending item per function call.
<rdar://problem/16270007>, <rdar://problem/16032150> 

llvm-svn: 203449