to "#ifdef PNG_HANDLE_AS_UNKNOWN_SUPPORTED", to make the png_set_keep
    mechanism available for ignoring known chunks even when not saving
    unknown chunks.

about calling png_set_IHDR() multiple times and about the order
of color samples in the tRNS chunk.

about calling png_set_IHDR() multiple times and about the order
of color samples in the tRNS chunk.

about using png_set_io_ptr() in configure scripts for detecting libpng

Broke several remaining "if () statement;" and "else statement;" into
two lines.

since there's only one makefile, so users can just type "make"
instead of "make -f makefile.std".

based on contrib/gregbook/rpng2-x

png_combine_row() and png_read_finish_row() are not used by progressive
PNG readers.

This should be handled in the APNG fork instead of in libpng proper.
This reverts commit ee59a9f9.

This forces the prev_row array to be cleared before the first
row of each image and interlace pass.

Added advice about setting pointers to NULL after png_free(),
capitalized sentences, reformatted long comments in libpng style.

(from the git master branch)

Should refer to "pngwin.def" instead of "pngw32.def"

(should refer to pngwin.def not pngw32.def)

There are too many master directories floating around now...

It is no longer used since the MMX support was removed.