Some control file improvements

Removed libcjs0c dependence already added automatically by
${shlibs:Depends} from libcjs-dev used on build.
Removed libmuffin0 dependence already added automatically by
${shlibs:Depends} from libmuffin-dev used on build.
These will include also any cjs and muffin libraries version increase
(also in packages name) without change control file.
Added gksu as recommends, used by cinnamon-settings-users.