bash could not parse (Bug report by Nelson Beebe).

not info_ptr.

png_handle_pCAL() (Bug report by John Regehr).

    are derived from previous versions.
Removed much of the long list of previous versions from png.h and
    libpng.3.

attempts to ignore the errors in the code aren't quite enough to
deal with the 'channel selection' encoding added to libpng 1.7; abort.

functions. They unnecessarily duplicate png_set_filler() and png_set_add_alpha()
which now work properly with 16-bit images.

input that was made in version 1.6.17beta01, to preserve legacy
behavior even though it was incorrect.  Instead, added new API
png_set_filter_16() and png_set_add_alpha_16() that set a flag to
make png_do_read_filter() interpret the filler bytes properly.