aspell: add all missing official dictionaries

From:

  https://ftp.gnu.org/gnu/aspell/dict/0index.html

Use a specialized function, buildOfficialDict to specialize builds of
official aspell dictionaries and add an update script.

pkgs/development/libraries/aspell/default.nix

@@ -2,6 +2,17 @@
 , searchNixProfiles ? true
 }:
 
+let
+
+  # Source for u-deva.cmap and u-deva.cset: use the Marathi
+  # dictionary like Debian does.
+  devaMapsSource = fetchTarball {
+    url = "ftp://ftp.gnu.org/gnu/aspell/dict/mr/aspell6-mr-0.10-0.tar.bz2";
+    sha256 = "1v8cdl8x2j1d4vbvsq1xrqys69bbccd6mi03fywrhkrrljviyri1";
+  };
+
+in
+
 stdenv.mkDerivation rec {
   name = "aspell-0.60.6.1";
 
@@ -33,6 +44,13 @@ stdenv.mkDerivation rec {
     );
   '';
 
+  # Include u-deva.cmap and u-deva.cset in the aspell package
+  # to avoid conflict between 'mr' and 'hi' dictionaries as they
+  # both include those files.
+  postInstall = ''
+    cp ${devaMapsSource}/u-deva.{cmap,cset} $out/lib/aspell/
+  '';
+
   meta = {
     description = "Spell checker for many languages";
     homepage = http://aspell.net/;