chunk handling.

avoid ADLER32 evaluation.

to avoid a signed/unsigned compare in the preprocessor.

Fixed offsets in contrib/intel/intel_sse.patch

tarballs.

This reverts commit 97dfccb6.

pngwrite.c, pngunknown.c, and pngvalid.c.  Several warnings still remain
in pngvalid.c

flag definitions in pngpriv.h from 0xnnnn to 0xnnnnU and trivial changes
in png.c, pngread.c, and pngwutil.c.

flag definitions in pngpriv.h from 0xnnnn to 0xnnnnU.

Merged pngtest.c with libpng-1.7.0beta84/pngtest.c

ignore the ADLER32 checksum in the IDAT chunk as well as the chunk CRCs.

and pngrutil.c.

while decoding compressed data chunks.