being applied.

pngvalid still fails.

pngvalid still fails two tests, problem with row buffer.

to demonstrate chop_16_to_8

If this is not enabled, png_set_strip_16() and png_do_scale_16_to_8()
aren't built.

png_set_scale_16_to_8 from pngpriv.h

and fix some other small typos.

    1.5.3beta06
  Also removed a spurious (totally unused and confusing) member 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.

not libpng version for presence of png_set_chop_16_to_8(), in pngvalid.c

by disabling PNG_CHOP_16_TO_8_SUPPORTED

called.

Fixed some compiliation problems with scaling options.

outside of an unknown-chunk block in png.h because they are also
needed for other uses.

to get the same (inaccurate) output as libpng-1.5.2 and earlier.