upgpkg: libpng12 1.2.51-1

new upstream release

git-svn-id: file:///srv/repos/svn-community/svn@107096 9fca08f4-af9d-4005-b8df-a31f2cc04f65
archrelease: copy trunk to community-i686, community-x86_64

git-svn-id: file:///srv/repos/svn-community/svn@107097 9fca08f4-af9d-4005-b8df-a31f2cc04f65