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.

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.

based on contrib/gregbook/rpng2-x

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

(from the git master branch)

(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.