109.32.00

- Improved the batching of `Pipe.fold` and other `Pipe` functions that handle batches.

  Previously, such functions used a loop with `Pipe.read`.  This didn't
  batch as well as it might.  If values were put in the pipe after the
  `read` becomes determined but before the values are handled, then they
  wouldn't be handled until the next batch.  Now, batching functions use
  `values_available` and then pull elements out of the pipe
  synchronously after waking up.  This makes the batch as large as
  possible.