It had been put inside the png_debug2() statement.

PNG_UNKNOWN_CHUNK_SUPPORTED should be PNG_HANDLE_AS_UNKNOWN_SUPPORTED.

in pngwutil.c, that was recently added by mistake.

with information that the NULL dereference bug first appeared in libpng-0.95.

in png_set_text-2().  Bug discovered by Evan Rouault, using cochinelle.

in png.c (suggested by Peter Breitenlohner)

from the new call to png_read_gray_to_rgb() (bug introduced in
libpng-1.4.0beta67). (Patch contributed by Alam Arias)

The AVG and PAETH filters will never be selected for the first
row, so we need not test them.

and png_write_png().

outside of the PNG_READ|WRITE_ANCILLARY_CHUNK_SUPPORTED blocks, where
they did not really belong.  Updated CHANGES and ANNOUNCE.

It is not of any use in libpng-1.4.0; it was only to support binary
compatibility between some old libpng-1.0.x versions.  It should have
been removed from libpng-1.2.x as well but it is too late for that now.

    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.