Make a couple of changes to help improve server performance:

- Update the server code to replace simple uses of ReentrantLock involving
  {lock, doSomething, unlock} in the same method to use the synchronized
  keyword instead of a ReentrantLock object.  Using the synchronized keyword is
  actually a little faster, and also simplifies the code since it's no longer
  necessary to use a finally block to ensure that the lock is released.

- Update the AsynchronousTextWriter to use the LinkedBlockingQueue.drainTo()
  method to attempt to get multiple messages at once, rather than always using
  poll() to get one message at a time.