mldonkey: fix the build

This fixes the build by pulling a patch currently under review.
This patch is also currently used by Gentoo.

pkgs/applications/networking/p2p/mldonkey/default.nix

@@ -1,4 +1,4 @@
-{ lib, stdenv, fetchurl, ocamlPackages, zlib }:
+{ lib, stdenv, fetchurl, fetchpatch, ocamlPackages, zlib }:
 
 stdenv.mkDerivation rec {
   pname = "mldonkey";
@@ -9,6 +9,14 @@ stdenv.mkDerivation rec {
     sha256 = "b926e7aa3de4b4525af73c88f1724d576b4add56ef070f025941dd51cb24a794";
   };
 
+  patches = [
+    # Fixes C++17 compat
+    (fetchpatch {
+      url = "https://github.com/ygrek/mldonkey/pull/66/commits/20ff84c185396f3d759cf4ef46b9f0bd33a51060.patch";
+      hash = "sha256-MCqx0jVfOaLkZhhv0b1cTdO6BK2/f6TxTWmx+NZjXME=";
+    })
+  ];
+
   preConfigure = ''
     substituteInPlace Makefile --replace '+camlp4' \
       '${ocamlPackages.camlp4}/lib/ocaml/${ocamlPackages.ocaml.version}/site-lib/camlp4'