cleanup: Use up_cast.

git-svn-id: svn://tron.homeunix.org/simutrans/simutrans/trunk@7238 8aca7d54-2c30-db11-9de9-000461428c89
cleanup: Remove reduntant assignment of '\0'.

strcpy() already NUL-terminates the string.

git-svn-id: svn://tron.homeunix.org/simutrans/simutrans/trunk@7239 8aca7d54-2c30-db11-9de9-000461428c89
besch: Remove unnecessary special case from sound_writer_t::write_obj().

git-svn-id: svn://tron.homeunix.org/simutrans/simutrans/trunk@7240 8aca7d54-2c30-db11-9de9-000461428c89