Instead put them in pngtest-log.txt

in pngvalid.c

both the old and new files can now be optionally ignored, treated as errors
or warnings.

and print statements.

in libpng-manual.txt and libpng.3

objective of simplifying and improving the cosmetic appearance of png.h.

with the objective of improving the cosmetic appearance of png.h.

  Added some commentary about PNG_EXPORT in png.h and pngconf.h

(adapted from the UNUSED() macro in pngvalid.c by John Bowler)

and libpng.3

which returned the wrong type (png_uint_32 instead of png_uint_16).