FIX: bug in route-search which stopped search too early when all nodes in open list are overcrowded but not the current node

git-svn-id: svn://tron.homeunix.org/simutrans/simutrans/trunk@6485 8aca7d54-2c30-db11-9de9-000461428c89
Even less redraws

git-svn-id: svn://tron.homeunix.org/simutrans/simutrans/trunk@6486 8aca7d54-2c30-db11-9de9-000461428c89