plotutils: fix compilation with libpng15 (debian)

svn path=/nixpkgs/branches/libpng15/; revision=31837

pkgs/tools/graphics/plotutils/debian-patches.nix

···
+# Generated by debian-patches.sh from debian-patches.txt
+let
+  prefix = "http://patch-tracker.debian.org/patch/series/dl/plotutils/2.6-2";
+in
+[
+  {
+    url = "${prefix}/10_repair_postscript";
+    sha256 = "01v4a8mdhgsjxbf9a2xppx2lb05lp818v8afp5x2njv64wpgla8p";
+  }
+  {
+    url = "${prefix}/25_libpng15";
+    sha256 = "0l640rcsgc2mwpk7iqm0cf3b0gfcdgcn9wg4x88gaqxzx9rriph0";
+  }
+]

pkgs/tools/graphics/plotutils/debian-patches.txt

···
+plotutils/2.6-2
+10_repair_postscript
+25_libpng15

pkgs/tools/graphics/plotutils/default.nix

···
 
   buildInputs = [libpng];
 
+  patches = map fetchurl (import ./debian-patches.nix);
+
   configureFlags = "--enable-libplotter"; # required for pstoedit
 
   doCheck = true;