Autodetect pak when loading stuff without -objects but -load

git-svn-id: svn://tron.homeunix.org/simutrans/simutrans/trunk@6717 8aca7d54-2c30-db11-9de9-000461428c89
CHG: replace recursive algorithm for terraforming by list-based one - large speedup

git-svn-id: svn://tron.homeunix.org/simutrans/simutrans/trunk@6718 8aca7d54-2c30-db11-9de9-000461428c89