gscan2pdf: switch to current libtiff 4.6.0t

gscan2pdf is not compatible with libtiff 4.6.0
as published on https://libtiff.gitlab.io/libtiff/
and http://www.simplesystems.org/libtiff/ .
To fix the build, we used an older libtiff version
(see 9a579e14dd).

In the meantime, hylafaxplus developer Lee Howard
published a forked version "4.6.0t" of libtiff,
providing the missing tools, see
https://sourceforge.net/p/hylafax/mailman/message/58751879/ .
That fork is also suitable for gscan2pdf,
so the commit at hand changes the libtiff
version for gscan2pdf to use that fork.

pkgs/applications/graphics/gscan2pdf/default.nix

@@ -2,7 +2,7 @@
   # libs
   librsvg, sane-backends, sane-frontends,
   # runtime dependencies
-  imagemagick, libtiff_4_5, djvulibre, poppler_utils, ghostscript, unpaper, pdftk,
+  imagemagick, libtiff, djvulibre, poppler_utils, ghostscript, unpaper, pdftk,
   # test dependencies
   xvfb-run, liberation_ttf, file, tesseract }:
 
@@ -82,7 +82,7 @@ perlPackages.buildPerlPackage rec {
     wrapProgram "$out/bin/gscan2pdf" \
       --prefix PATH : "${sane-backends}/bin" \
       --prefix PATH : "${imagemagick}/bin" \
-      --prefix PATH : "${libtiff_4_5}/bin" \
+      --prefix PATH : "${libtiff}/bin" \
       --prefix PATH : "${djvulibre}/bin" \
       --prefix PATH : "${poppler_utils}/bin" \
       --prefix PATH : "${ghostscript}/bin" \
@@ -98,10 +98,7 @@ perlPackages.buildPerlPackage rec {
 
   nativeCheckInputs = [
     imagemagick
-    # Needs older libtiff version, because it stopped packageing tools like
-    # tiff2pdf and others in version 4.6. These tools are necessary for gscan2pdf.
-    # See commit f57a4b0ac1b954eec0c8def2a99e2a464ac6ff7a for in-depth explanation.
-    libtiff_4_5
+    libtiff
     djvulibre
     poppler_utils
     ghostscript

pkgs/top-level/all-packages.nix

@@ -5543,7 +5543,11 @@ with pkgs;
 
   grobi = callPackage ../tools/X11/grobi { };
 
-  gscan2pdf = callPackage ../applications/graphics/gscan2pdf { };
+  gscan2pdf = callPackage ../applications/graphics/gscan2pdf {
+    # needs this fork of libtiff, because original libtiff
+    # stopped packaging required tools with version 4.6
+    libtiff = libtiff_t;
+  };
 
   gsctl = callPackage ../applications/misc/gsctl { };