(dwachs) fix multithreading compile on Visual C++

git-svn-id: svn://tron.homeunix.org/simutrans/simutrans/trunk@6647 8aca7d54-2c30-db11-9de9-000461428c89
allow gui setting of lake generation on/off (option not saved yet pending interface overhaul)

git-svn-id: svn://tron.homeunix.org/simutrans/simutrans/trunk@6648 8aca7d54-2c30-db11-9de9-000461428c89
fixed bug in slope tools (also removed debug info committed earlier)

git-svn-id: svn://tron.homeunix.org/simutrans/simutrans/trunk@6649 8aca7d54-2c30-db11-9de9-000461428c89
FIX: deleting foundations at edge of map gave incorrect slope

git-svn-id: svn://tron.homeunix.org/simutrans/simutrans/trunk@6650 8aca7d54-2c30-db11-9de9-000461428c89