xml-security-c: should work on any unix

In practice its xalanc dependency will fail on platforms other than Linux
and Darwin, but if that gets fixed there's no reason this shouldn't work.

pkgs/development/libraries/xml-security-c/default.nix

@@ -28,7 +28,7 @@ stdenv.mkDerivation rec {
     homepage = http://santuario.apache.org/;
     description = "C++ Implementation of W3C security standards for XML";
     license = stdenv.lib.licenses.gpl2;
-    platforms = stdenv.lib.platforms.linux;
+    platforms = stdenv.lib.platforms.unix;
     maintainers = [ stdenv.lib.maintainers.jagajaga ];
   };
 }