This package has not been built since Fedora 15, having failed multiple mass rebuild cycles. As part of the normal process for retiring packages that have not successfully built, this package is scheduled to be removed from Fedora on or around the Fedora 18 branch date (August 7th). Please fix this as soon as possible.
The reason it's not building is that it assumes an ancient version of libpng. It could probably be fixed easily by updating to a current upstream release --- I see this is still at 1.6.10, but latest release at https://sourceforge.net/projects/pmt/files/pngcrush/ is 1.7.34.
http://koji.fedoraproject.org/koji/buildinfo?buildID=345182