Adding oath-toolkit and xmlsec

I added xmlsec to make it work with oath-toolkit (to build one extra tool
there, that I don't need), but I couldn't make it work together.

pkgs/development/libraries/xmlsec/default.nix

@@ -0,0 +1,24 @@
+{ stdenv, fetchurl, libxml2, gnutls, libxslt, pkgconfig, libgcrypt, libtool }:
+
+let
+  version = "1.2.19";
+in
+stdenv.mkDerivation rec {
+  name = "xmlsec-${version}";
+
+  src = fetchurl {
+    url = "http://www.aleksey.com/xmlsec/download/xmlsec1-${version}.tar.gz";
+    sha256 = "1h5ar0h8n0l8isgic82w00cwfpw7i9wxw17kbdb6q3yvzb4zgj1g";
+  };
+
+  buildInputs = [ libxml2 gnutls libxslt pkgconfig libgcrypt libtool ];
+
+  enableParallelBuilding = true;
+
+  meta = {
+    homepage = http://www.aleksey.com/xmlsec;
+    description = "XML Security Library in C based on libxml2";
+    license = "MIT";
+    platforms = stdenv.lib.platforms.linux;
+  };
+}