Use pkg-config for detecting libpng and libbz2 also. * builds/unix/configure.raw (HAVE_PKG): New variable. Search for libbz2 using `pkg-config'; s/BZ2/BZIP2/. Search for libpng using `pkg-config'. Fix definition of `LIBHARFBUZZ' variable. * builds/unix/freetype-config.in ($libs): Updated. * builds/unix/freetype2.in: Add `URL' field. Update `Requires.private' and `Libs.private'. * builds/unix/unix-def.in: Updated.