Log Message:
Changes 6.8.8.5:
* Fix case where an image moment might have a mass of 0 or a Hu moment might
  be 0.
* Enhance the TXT coder to read RGB percent values (e.g. 10.008%).
* Fixed new "-define png:swap-bytes" option (reference
  http://www.imagemagick.org/discourse-server/viewtopic.php?f=2&t=24818).