upgpkg: lib32-libpng 1.6.8-1

upstream update

git-svn-id: file:///srv/repos/svn-community/svn@104779 9fca08f4-af9d-4005-b8df-a31f2cc04f65
archrelease: copy trunk to multilib-x86_64

git-svn-id: file:///srv/repos/svn-community/svn@104780 9fca08f4-af9d-4005-b8df-a31f2cc04f65