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).

Certain optional gcc warning flags resulted in warnings in libpng code.
With these changes only -Wconversion and -Wcast-qual cannot be turned on.
Changes are trivial rearrangements of code.  -Wconversion is not possible
for pngrutil.c (because of the widespread use of += et al on variables
smaller than (int) or (unsigned int)) and -Wcast-qual is not possible
with pngwio.c and pngwutil.c because the 'write' callback and zlib
compression both fail to declare their input buffers with 'const'.

Moved reading of file signature into png_read_sig (Cosmin)
Fixed atomicity of chunk header serialization (Cosmin)
Added test for io_state in pngtest.c (Cosmin)
Added "#!/bin/sh" at the top of contrib/pngminim/*/gather.sh scripts.