FIX crash if lightmap is only one pixel

git-svn-id: svn://tron.homeunix.org/simutrans/simutrans/trunk@6775 8aca7d54-2c30-db11-9de9-000461428c89
CODE: templated create_slot as function

git-svn-id: svn://tron.homeunix.org/simutrans/simutrans/trunk@6776 8aca7d54-2c30-db11-9de9-000461428c89
CODE: make templated set_slot and use it

git-svn-id: svn://tron.homeunix.org/simutrans/simutrans/trunk@6777 8aca7d54-2c30-db11-9de9-000461428c89
FIX crash when loading old savegames

git-svn-id: svn://tron.homeunix.org/simutrans/simutrans/trunk@6778 8aca7d54-2c30-db11-9de9-000461428c89
CODE implement templated get_slot and use it

git-svn-id: svn://tron.homeunix.org/simutrans/simutrans/trunk@6779 8aca7d54-2c30-db11-9de9-000461428c89
sqapi: export building/tree/way besch's

git-svn-id: svn://tron.homeunix.org/simutrans/simutrans/trunk@6780 8aca7d54-2c30-db11-9de9-000461428c89