to check info_ptr members instead of the contents of the returned parameters.

to avoid bogus complaints about filter method.

a 16-bit int (assuming height immediately follows width).

PNG_UNKNOWN_CHUNKS_SUPPORTED should be PNG_HANDLE_AS_UNKNOWN_SUPPORTED

that was recently added to png_write_find_filter() in pngwutil.c

into png.h and revised the documenatation (in the libpng style section) about
placement of prototypes.

in png_set_text_2() (bug introduced in libpng-0.95, discovered by Evan Rouault)

(suggested by Peter Breitenlohner)