cracklib: add license

pkgs/development/libraries/cracklib/default.nix

···
   meta = with stdenv.lib; {
     homepage    = https://github.com/cracklib/cracklib;
     description = "A library for checking the strength of passwords";
+    license = licenses.lgpl21; # Different license for the wordlist: http://www.openwall.com/wordlists
     maintainers = with maintainers; [ lovek323 ];
     platforms   = platforms.unix;
   };