sqapi: export ribi of ways

git-svn-id: svn://tron.homeunix.org/simutrans/simutrans/trunk@6668 8aca7d54-2c30-db11-9de9-000461428c89
FIX: sqapi exporting of ways was pretty much broken

git-svn-id: svn://tron.homeunix.org/simutrans/simutrans/trunk@6669 8aca7d54-2c30-db11-9de9-000461428c89
FIX: clipping region was wrong if tile is near lower border of screen - buildings shined through bridges

git-svn-id: svn://tron.homeunix.org/simutrans/simutrans/trunk@6670 8aca7d54-2c30-db11-9de9-000461428c89