Use autoreconf to regenerate the build system to fix build errors on
newer macOS versions. Patch configure.ac to remove an obsolete bit to
eliminate a warning printed when configure was run. Modernize checksums.
Change "Mac OS X" to "macOS" in descriptions. Rewrite master_sites to
avoid redirects. Rewrite depends_lib to ensure dependencies from
MacPorts get used. Remove platforms which was set to its default value.
