Log Message:
Changes 0.6.1:
* Upgraded cexcept to version 2.0.1.
* Added a configure script, to be used instead of unix-secure.mak.
* Fixed a build issue that occured when using libpng from the system.
* Fixed processing when image reduction yields an output larger than
  the original.
* Fixed behavior of -preserve.
* Removed displaying of partial progress when abandoning IDATs under
  the -v option.  The percentages displayed were not very accurate.

Changes 0.6:
* Upgraded libpng to version 1.2.29-optipng [private]
* Implemented grayscale(alpha)-to-palette reductions.
* Improved conversion of bKGD info during RGB-to-palette reductions.
* Fixed conversion of bKGD and tRNS during 16-to-8-bit reductions.
* Added support for compressed BMP (incl. PNG-compressed BMP, you bet!)
* Improved the speed of reading raw PNM files.
* Recognized PNG digital signatures (dSIG) and disabled optimization
  in their presence, to preserve their integrity.
* Allowed the user to enforce the optimization of dSIG'ed files.
* Recognized APNG animation files and disabled reductions to preserve
  their integrity.
* Added the -snip option, to allow the user to "snip" one image out of
  a multi-image file, such as animated GIF, multi-page TIFF, or APNG.
* Improved recovery of PNG files with incomplete IDAT.
* Fixed a crash triggered by the use of -log on some platforms.
* Fixed behavior of -out and -dir when the input is already optimized.
* Provided more detailed image information at the start of processing.
* Provided a more detailed summary at the end of processing, under the
  presence of the -v option and/or the occurence of exceptional events.