Log Message:
Changes 6.6.6.5:
* Make the PNG encoder always rebuild the palette, to avoid losing
  transparency when it is out of sync with the pixel data.
  Eliminated CompressColormapTransFirst() since the palette is already
  compressed and sorted by opacty now when it's recreated.
* Account for virtual canvas for the -flip / -flop options.
* Also for -transpose and transverse options
* Support -metric fuzz option.

Changes 6.6.6.4:
* Replace IsMagickColorSimilar() which provides the Fuzz Factor threshold
  function.  Note function does not calculate 'distance' in total but
  short-circuits when threshold is reached for faster processing.
* Ordered Dithered handling of Alpha channel was incorrect - fixing
  Bug was introduced v6.6.5-6

Changes 6.6.6.3:
* Fixed two more cases where the PNG encoder lost transparency.

Changes 6.6.6.2:
* Affine multiplication reversed when translating.

Changes 6.6.6.2:
* Revised the "c7x7b" and "c7x7w" ordered-dither maps to be \ 
complementary
  to each other.

Changes 6.6.6.1:
* Add support for -evaluate-sequence median.

Changes 6.6.6.0:
* Fixed two more cases where the PNG encoder lost transparency.
* The policy.xml sets not-to-exceed resource values (e.g. policy memory limit
  1GB, -limit 2GB exceeds policy maximum so memory limit is 1GB).
* Support NCC (normalized cross correlation) compare metric.