Log Message:
Update to 1.5.4:

Version 1.5.3beta11 [June 11, 2011]
  Fixed png_handle_sCAL which is broken in 1.5; added sCAL to pngtest.png
  Revised documentation about png_set_user_limits() to say that it also affects
    png writing.
  Revised handling of png_set_user_limits() so that it can increase the
    limit beyond the PNG_USER_WIDTH|HEIGHT_MAX; previously it could only
    reduce it.
  Make the 16-to-8 scaling accurate. Dividing by 256 with no rounding is
    wrong (high by one) 25% of the time. Dividing by 257 with rounding is
    wrong in 128 out of 65536 cases. Getting the right answer all the time
    without division is easy.
  Added "_SUPPORTED" to the PNG_WRITE_CUSTOMIZE_ZTXT_COMPRESSION macro.
  Added projects/owatcom, an IDE project for OpenWatcom to replace
    scripts/makefile.watcom.  This project works with OpenWatcom 1.9. The
    IDE autogenerates appropriate makefiles (libpng.mk) for batch processing.
    The project is configurable, unlike the Visual Studio project, so long
    as the developer has an awk.
  Changed png_set_gAMA to limit the gamma value range so that the inverse
    of the stored value cannot overflow the fixed point representation,
    and changed other things OpenWatcom warns about.
  Revised pngvalid.c to test PNG_ALPHA_MODE_SUPPORTED correctly. This allows
    pngvalid to build when ALPHA_MODE is not supported, which is required if
    it is to build on libpng 1.4.
  Removed string/memory macros that are no longer used and are not
    necessarily fully supportable, particularly png_strncpy and png_snprintf.
  Added log option to pngvalid.c and attempted to improve gamma messages.

Version 1.5.3 [omitted]
  People found the presence of a beta release following an rc release
    to be confusing; therefore we bump the version to libpng-1.5.4beta01
    and there will be no libpng-1.5.3 release.

Version 1.5.4beta01 [June 14, 2011]
  Made it possible to undefine PNG_READ_16_TO_8_ACCURATE_SCALE_SUPPORTED
    to get the same (inaccurate) output as libpng-1.5.2 and earlier.
  Moved definitions of PNG_HAVE_IHDR, PNG_AFTER_IDAT, and PNG_HAVE_PLTE
    outside of an unknown-chunk block in png.h because they are also
    needed for other uses.

Version 1.5.4beta02 [June 14, 2011]
  Fixed and clarified LEGACY 16-to-8 scaling code.
  Added png_set_chop_16() API, to match inaccurate results from previous
    libpng versions.
  Removed the ACCURATE and LEGACY options (they are no longer useable)
  Use the old scaling method for background if png_set_chop_16() was
    called.
  Made png_set_chop_16() API removeable by disabling PNG_CHOP_16_TO_8_SUPPORTED

Version 1.5.4beta03 [June 15, 2011]
  Fixed a problem in png_do_expand_palette() exposed by optimization in
    1.5.3beta06
  Also removed a spurious and confusing "trans" member \ 
("trans") from png_info.
  The palette expand optimization prevented expansion to an intermediate RGBA
    form if tRNS was present but alpha was marked to be stripped; this exposed
    a check for tRNS in png_do_expand_palette() which is inconsistent with the
    code elsewhere in libpng.
  Correction to the expand_16 code; removed extra instance of
    png_set_scale_16_to_8 from pngpriv.h

Version 1.5.4beta04 [June 16, 2011]
  Added a missing "#ifdef PNG_READ_BACKGROUND_SUPPORTED/#endif" in \ 
pngrtran.c
  Added PNG_TRANSFORM_CHOP_16 to the high-level read transforms.
  Made PNG_READ_16_TO_8_ACCURATE_SCALE configurable again.  If this is
    not enabled, png_set_strip_16() and png_do_scale_16_to_8() aren't built.
  Revised contrib/visupng, gregbook, and pngminim to demonstrate chop_16_to_8

Version 1.5.4beta05 [June 16, 2011]
  Renamed png_set_strip_16() to png_set_scale_16() and renamed
    png_set_chop_16() to png_set_strip(16) in an attempt to minimize the
    behavior changes between libpng14 and libpng15.

Version 1.5.4beta06 [June 18, 2011]
  Fixed new bug that was causing both strip_16 and scale_16 to be applied.

Version 1.5.4beta07 [June 19, 2011]
  Fixed pngvalid, simplified macros, added checking for 0 in sCAL.
    The ACCURATE scale macro is no longer defined in 1.5 - call the
    png_scale_16_to_8 API.  Made sure that PNG_READ_16_TO_8 is still defined
    if the png_strip_16_to_8 API is present.  png_check_fp_number now
    maintains some state so that positive, negative and zero values are
    identified.  sCAL uses these to be strictly spec conformant.

Version 1.5.4beta08 [June 23, 2011]
  Fixed pngvalid if ACCURATE_SCALE is defined.
  Updated scripts/pnglibconf.h.prebuilt.

Version 1.5.4rc01 [June 30, 2011]
  Define PNG_ALLOCATED to "restrict" only if MSC_VER >= 1400.

Version 1.5.4 [July 7, 2011]
  no changes.