ENG-4870: Don't terminate ack tracking thread if the thread was interrupted.
Merge pull request #605 from VoltDB/ENG-4870-stream

ENG-4870: Don't terminate ack tracking thread if the thread was interrupted
Add PDFs of undated documentation to s/w kit.
Merge branch 'master' of github.com:VoltDB/voltdb into ENG-4696-truncate