libssh: temporarily patch to fix x2goclient

See <https://red.libssh.org/issues/194>:

  "In libssh 0.7.0, ssh_forward_listen() is present in the headers as
  a deprecated function, but it is not actually present in the code.
  This appears to have been introduced in commit 5229253f."

pkgs/development/libraries/libssh/default.nix

@@ -34,6 +34,8 @@ stdenv.mkDerivation rec {
     sha256 = "1wfrdqhv97f4ycd9bcpgb6gw47kr7b2iq8cz5knk8a6n9c6870k0";
   };
 
+  patches = [ ./0001-Reintroduce-ssh_forward_listen-Fixes-194.patch ];
+
   postPatch = ''
     # Fix headers to use libsodium instead of NaCl
     sed -i 's,nacl/,sodium/,g' ./include/libssh/curve25519.h src/curve25519.c