Log Message:
Update to 1.5.1beta06:

Version 1.5.1beta02 [January 14, 2011]
  Fixed a bug in handling of interlaced images (bero at arklinux.org).
  Updated CMakeLists.txt (Clifford Yapp)

Version 1.5.1beta03 [January 14, 2011]
  Fixed typecasting of some png_debug() statements (Cosmin)

Version 1.5.1beta04 [January 16, 2011]
  Updated documentation of png_set|get_tRNS() (Thomas Klausner).
  Mentioned in the documentation that applications must #include "zlib.h"
    if they need access to anything in zlib.h, and that a number of
    macros such as png_memset() are no longer accessible by applications.
  Corrected pngvalid gamma test "sample" function to access all of the \ 
color
    samples of each pixel, instead of sampling the red channel three times.
  Prefixed variable names index, div, exp, gamma with "png_" to avoid \ 
"shadow"
    warnings, and (mistakenly) changed png_exp() to exp().

Version 1.5.1beta05 [January 16, 2011]
  Changed variable names png_index, png_div, png_exp, and png_gamma to
    char_index, divisor, exp_b10, and gamma_val, respectively, and
    changed exp() back to png_exp().

Version 1.5.1beta06 [January 20, 2011]
  Prevent png_push_crc_skip() from hanging while reading an unknown chunk
    or an over-large compressed zTXt chunk with the progressive reader.
  Eliminated more GCC "shadow" warnings.
  Revised png_fixed() in png.c to avoid compiler warning about reaching the
    end without returning anything.