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

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

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.

to catch library and header mismatch, also found at the end of pngtest.c.

that CCP writes to standard output by default (Martin Banky).

Studio 2010 (John Bowler).

and shortening problems on assignment but also a few difficult to optimize
(for GCC) loops (John Bowler).

literal pointers declare them (John Bowler).
Many APIs did not change their arguments but were not declared using
PNG_CONST.  This change corrects this.  In a few cases APIs that return
constant string literal pointers have also been changed to declare this.
Unlike the argument change this may require app changes; however the
results could never be written to (the app would crash on some platforms
where strings are not writable), so this seems advisable.