Use '\0', not NULL, to assign a NUL-char.

git-svn-id: svn://tron.homeunix.org/simutrans/simutrans/trunk@7149 8aca7d54-2c30-db11-9de9-000461428c89
Correct pointless assignment to temporary objects.

git-svn-id: svn://tron.homeunix.org/simutrans/simutrans/trunk@7150 8aca7d54-2c30-db11-9de9-000461428c89
CODE: dr_time() returns uint32, make time arithmetic robust against overflow

git-svn-id: svn://tron.homeunix.org/simutrans/simutrans/trunk@7151 8aca7d54-2c30-db11-9de9-000461428c89
FIX: make convoi maximal loading time robust against time overflow

git-svn-id: svn://tron.homeunix.org/simutrans/simutrans/trunk@7152 8aca7d54-2c30-db11-9de9-000461428c89
CODE change signed/unsigned comparison

git-svn-id: svn://tron.homeunix.org/simutrans/simutrans/trunk@7153 8aca7d54-2c30-db11-9de9-000461428c89
remove unused parameter

git-svn-id: svn://tron.homeunix.org/simutrans/simutrans/trunk@7154 8aca7d54-2c30-db11-9de9-000461428c89