The UNIX builds for Debian and Redhat/RPM now default to using the
builtin PNG and zlib libraries. This will ease issues at release
time, since we don't need to worry about those libraries being
present on the destination systems.
git-svn-id: svn://svn.code.sf.net/p/stella/code/trunk@2054 8b62c5a3-ac7e-4cc8-8f21-d9a121418aba