[png-mng-implement] libpng-1.2.25beta03 available

[Glenn Randers-P. <gl...@gm...>]

Libpng-1.2.25beta03 is available at
ftp://ftp.simplesystems.org/pub/png-group/src/
and at
http://libpng.sf.net/

It fixes a bunch of bugs reported by David Hill, uncovered by Coverity.

Libpng-1.2.25rc01 and libpng-1.0.31rc01 are obsolete.

Glenn