Log Message:
Update to 0.72. From the release announcement:

This is a bugfix release to address a few reported issues and also a few
issues that were discovered via my own testing.

    * Add a helper method which ensures all data is flushed to disk
    * Added additional error handling to prevent malformed DHT messages
      crashing the library
    * Fixed issue when zeroing unused bits for torrents with an exact
      multiple of 32 pieces
    * Fixed issue where data could be written to the wrong file if a file
      with the same name existed in multiple torrents
    * Fixed the handling of torrents where the last file(s) are of zero
      length
    * Fixed regression with global download rate limiting
    * Fixed a performance regression with the new piece picking pipeline
      which resulted in lots of CPU cycles being used up on peers which
      have not sent an unchoke message