directories to be specified through the environment variable
ASPELL_EXTRA_DICT_DIRS. This way dictionaries don't have to be
installed into aspell's prefix. Instead you can just set
ASPELL_EXTRA_DICT_DIRS to $HOME/.nix-profile/lib/aspell and install
dictionaries separately with nix-env (e.g. "nix-env -i
aspell-dict-nl").
* Added a bunch of Aspell dictionaries. Additional dictionaries can
be added easily in development/libraries/aspell/dictionaries.nix.
svn path=/nixpkgs/trunk/; revision=9512
