hylafaxplus: patch source to fix build with libtiff 4.5

After libtiff's update to 4.5 in

https://github.com/NixOS/nixpkgs/commit/4d4af86db63955be68118f1507ce51e576b88016

hylafaxplus fails to build.
This is caused by libtiff 4.5 removing many exported symbols.
See this discussion for more details:

https://gitlab.com/libtiff/libtiff/-/issues/504

The next hylafaxplus relese will contain updated code such that
the missing code is simply added to the hylafaxplus codebase:

https://sourceforge.net/p/hylafax/HylaFAX+/2695/

To get hylafaxplus up and working again,
the commit at hand applies the corresponding patch.
Since Sourceforge doesn't permit to download patches
directly, we instead fetch the patch from Gentoo.

pkgs/servers/hylafaxplus/default.nix

@@ -72,6 +72,16 @@ stdenv.mkDerivation {
   patches = [
     # adjust configure check to work with libtiff > 4.1
     ./libtiff-4.patch
+    # fix missing exports in libtiff 4.5+
+    # https://gitlab.com/libtiff/libtiff/-/issues/504
+    # can probably be dropped with next hylafaxplus release
+    (fetchurl {
+      name = "hylafaxplus-7.0.6-tiff-4.5.0.patch";
+      url = "https://dev.gentoo.org/~sam/distfiles/net-misc/hylafaxplus/hylafaxplus-7.0.6-tiff-4.5.0.patch.xz";
+      downloadToTemp = true;
+      postFetch = ''xz -d < $downloadedFile > $out'';
+      hash = "sha256-koZvvzlgZHcANVaYdewnuLARz2TTeyDZRjm0EYWzsmk=";
+    })
   ];
   # Note that `configure` (and maybe `faxsetup`) are looking
   # for a couple of standard binaries in the `PATH` and