libwmf: fix some security issues

The added patches (sourced from Debian) fixes the following security
issues:

  - CVE-2006-3376
  - CVE-2009-1364
  - CVE-2015-0848
  - CVE-2015-4588
  - CVE-2015-4695
  - CVE-2015-4696

pkgs/development/libraries/libwmf/default.nix

@@ -11,6 +11,11 @@ stdenv.mkDerivation {
 
   buildInputs = [ zlib imagemagick libpng pkgconfig glib freetype libjpeg libxml2 ];
 
+  patches = [
+    ./CVE-2006-3376.patch ./CVE-2009-1364.patch
+    ./CVE-2015-0848+4588+4695+4696.patch
+  ];
+
   meta = {
     description = "WMF library from wvWare";
   };