Comment 25 for bug 1690519

I created a brach for testing this on OSX:
https://code.launchpad.net/~widelands-dev/widelands/osx-malloc-check

I still get +/ random like carsh in std fucntions when e.g. iterating over
WL objecs. I will try to add more and more assertions to that branch
to narrow down the problem.