[jvstm-lf] Buffer sending commit requests. Lock-based impl.
[jvstm-lf] Broadcast commit request asynchronously

  This new feature enables the committer to move on to the helping phase even
  if the broadcast of its own commit request takes some time.  With this
  change, I expect to change some of the time spend in the commit from the
  "waiting caused by the synchronous broadcast" to the "helping of any
  incoming requests ahead of 'mine'".
[jvstm-lf] LockFreeTransaction with commit statistics
[jvstm-lf] More commit stats (drill down on T4) and simplify tryCommit (don't repeat handling same request)
[jvstm-lf] Receive commit request asynchronously
[jvstm-lf] Don't yield() when waiting for next request to arrive