FIX: compile for SDL2

git-svn-id: svn://tron.homeunix.org/simutrans/simutrans/trunk@6696 8aca7d54-2c30-db11-9de9-000461428c89
removed unused parameter warning in simhalt.cc

git-svn-id: svn://tron.homeunix.org/simutrans/simutrans/trunk@6697 8aca7d54-2c30-db11-9de9-000461428c89
FIX: depot gui clipped text

git-svn-id: svn://tron.homeunix.org/simutrans/simutrans/trunk@6698 8aca7d54-2c30-db11-9de9-000461428c89
FIX: don't allow dragging to set heights outside limits

git-svn-id: svn://tron.homeunix.org/simutrans/simutrans/trunk@6699 8aca7d54-2c30-db11-9de9-000461428c89