Add new kgraphviewer and massif-visualizer packages

I chose the unstable versions because the stable versions
seemed too outdated to me. They work with kde 4.12 anyway.

pkgs/development/tools/analysis/massif-visualizer/default.nix

@@ -0,0 +1,20 @@
+{ stdenv, fetchurl, kdelibs, kgraphviewer, gettext }:
+
+stdenv.mkDerivation rec {
+  name = "massif-visualizer-${version}";
+  version = "0.3.90";
+
+  src = fetchurl {
+    url = "mirror://kde/unstable/massif-visualizer/${version}/src/${name}.tar.xz";
+    sha256 = "9940fa90137ca5eef08b9ec220825fadbf03db423a670a2c7fe3edab271d9922";
+  };
+
+  buildInputs = [ kdelibs kgraphviewer gettext ];
+
+  meta = with stdenv.lib; {
+    description = "Tool that visualizes massif data generated by valgrind";
+    license = licenses.gpl2;
+    platforms = platforms.linux;
+    maintainers = [ maintainers.lethalman ];
+  };
+}