gnuplot darwin: optional gnuplot_aquaterm variant

This variant uses the more Mac-friendly aqua driver, but it requires
that you separately install the AquaTerm package.

Note that AquaTerm is open source and could perhaps be later included
as a nix derivation. If that happens, it would be nice to remove the
gnuplot_aquaterm top-level attribute and just make it the default.

pkgs/tools/graphics/gnuplot/default.nix

@@ -6,6 +6,7 @@
 , libXt ? null
 , libXpm ? null
 , libXaw ? null
+, aquaterm ? false
 , wxGTK ? null
 , pango ? null
 , cairo ? null
@@ -24,15 +25,18 @@ stdenv.mkDerivation rec {
     sha256 = "1xd7gqdhlk7k1p9yyqf9vkk811nadc7m4si0q3nb6cpv4pxglpyz";
   };
 
+  withX = libX11 != null && !aquaterm;
+
   buildInputs =
-    [ zlib gd texinfo readline emacs lua texLive libX11 libXt libXpm libXaw
+    [ zlib gd texinfo readline emacs lua texLive
       pango cairo pkgconfig makeWrapper ]
+    ++ stdenv.lib.optionals withX              [ libX11 libXpm libXt libXaw ]
     # compiling with wxGTK causes a malloc (double free) error on darwin
     ++ stdenv.lib.optional (!stdenv.isDarwin) wxGTK;
 
-  configureFlags = if libX11 != null then ["--with-x"] else ["--without-x"];
+  configureFlags = if withX then ["--with-x"] else ["--without-x"];
 
-  postInstall = stdenv.lib.optionalString (libX11 != null) ''
+  postInstall = stdenv.lib.optionalString withX ''
     wrapProgram $out/bin/gnuplot \
        --prefix PATH : '${gnused}/bin' \
        --prefix PATH : '${coreutils}/bin' \

pkgs/top-level/all-packages.nix

@@ -1003,6 +1003,9 @@ let
       else stdenv;
   };
 
+  # must have AquaTerm installed separately
+  gnuplot_aquaterm = gnuplot.override { aquaterm = true; };
+
   gnused = callPackage ../tools/text/gnused { };
 
   gnutar = callPackage ../tools/archivers/gnutar { };