Log Message:
Update to 1.2.20:

version 1.2.20beta01 [August 19, 2007]
  Fixed problem with compiling pnggccrd.c on Intel-Apple platforms.
  Added PNG_NO_ERROR_TEXT feature, with demo in contrib/pngminim
  Removed define PNG_WARN_UNINITIALIZED_ROW 1 /* 0: warning; 1: error */
    because it caused some trouble.

version 1.2.20beta02 [August 20, 2007]
  Avoid compiling pnggccrd.c on Intel-Apple platforms.

version 1.2.20beta03 [August 20, 2007]
  Added "/D PNG_NO_MMX_CODE" to the non-mmx builds of projects/visualc6
    and visualc71.

version 1.2.20beta04 [August 21, 2007]
  Revised pngvcrd.c for improved efficiency (Steve Snyder).

version 1.2.20rc1 [August 23, 2007]
  Revised pngconf.h to set PNG_NO_MMX_CODE for gcc-3.x compilers.

version 1.2.20rc2 [August 27, 2007]
  Revised scripts/CMakeLists.txt
  Revised #ifdefs to ensure one and only one of pnggccrd.c, pngvcrd.c,
    or part of pngrutil.c is selected.

version 1.2.20rc3 [August 30, 2007]
  Remove a little more code in pngwutil.c when PNG_NO_WRITE_FILTER is selected.
  Added /D _CRT_SECURE_NO_WARNINGS to visual6c and visualc71 projects.
  Compile png_mmx_support() in png.c even when PNG_NO_MMX_CODE is defined.
  Restored a "superfluous" #ifdef that was removed from 1.2.20rc2 \ 
pnggccrd.c,
    breaking the png_mmx_support() function.

version 1.2.20rc4 [September 1, 2007]
  Removed Intel contributions (MMX, Optimized C).

version 1.2.20rc5 [September 2, 2007]
  Restored configure and Makefile.in to rc3 and put a snippet of code in
    pnggccrd.c, to ensure configure makes the same PNG_NO_MMX_CODE selection

version 1.2.20rc6 [September 2, 2007]
  Fixed bugs in scripts/CMakeLists.txt
  Removed pngvcrd.c references from msvc projects.

version 1.0.28 and 1.2.20 [September 8, 2007]
  Removed "(NO READ SUPPORT)" from png_get_header_version() string.