FIX: properly delete tunnel tiles, and do not leave empty tiles behind if smoke was on the tile

git-svn-id: svn://tron.homeunix.org/simutrans/simutrans/trunk@7063 8aca7d54-2c30-db11-9de9-000461428c89
FIX: mark image dirty if deleting ways

git-svn-id: svn://tron.homeunix.org/simutrans/simutrans/trunk@7064 8aca7d54-2c30-db11-9de9-000461428c89