FIX: double slopes had not double penalty during route search

git-svn-id: svn://tron.homeunix.org/simutrans/simutrans/trunk@7346 8aca7d54-2c30-db11-9de9-000461428c89
FIX (AthurDenture): Do not use barriers on MAC

git-svn-id: svn://tron.homeunix.org/simutrans/simutrans/trunk@7347 8aca7d54-2c30-db11-9de9-000461428c89
(AthurDenture) better autoconf recognisation on MAC

git-svn-id: svn://tron.homeunix.org/simutrans/simutrans/trunk@7348 8aca7d54-2c30-db11-9de9-000461428c89