FIX: squirrel call Raise_IdxError if rawget fails

git-svn-id: svn://tron.homeunix.org/simutrans/simutrans/trunk@7309 8aca7d54-2c30-db11-9de9-000461428c89
sqapi: update doc

git-svn-id: svn://tron.homeunix.org/simutrans/simutrans/trunk@7310 8aca7d54-2c30-db11-9de9-000461428c89
FIX: cities should not destroy public powerlines and transformers

git-svn-id: svn://tron.homeunix.org/simutrans/simutrans/trunk@7311 8aca7d54-2c30-db11-9de9-000461428c89