FIX: 32bit image counter for recoding/zooming images too

git-svn-id: svn://tron.homeunix.org/simutrans/simutrans/trunk@7438 8aca7d54-2c30-db11-9de9-000461428c89
FIX: (DrSuperGood) do not include index in checksum

git-svn-id: svn://tron.homeunix.org/simutrans/simutrans/trunk@7439 8aca7d54-2c30-db11-9de9-000461428c89