FIX: (jk271) fix cost display in depot

git-svn-id: svn://tron.homeunix.org/simutrans/simutrans/trunk@7422 8aca7d54-2c30-db11-9de9-000461428c89
FIX: sliced underground mode now ranges from actual lowest to actual highest ground

git-svn-id: svn://tron.homeunix.org/simutrans/simutrans/trunk@7423 8aca7d54-2c30-db11-9de9-000461428c89