reduce code duplication in haltestelle_t::add_grund

git-svn-id: svn://tron.homeunix.org/simutrans/simutrans/trunk@6354 8aca7d54-2c30-db11-9de9-000461428c89
FIX: save plainstrings of arbitrary lenght

git-svn-id: svn://tron.homeunix.org/simutrans/simutrans/trunk@6355 8aca7d54-2c30-db11-9de9-000461428c89
Updated for pak 128 german 0.5

git-svn-id: svn://tron.homeunix.org/simutrans/simutrans/trunk@6356 8aca7d54-2c30-db11-9de9-000461428c89