Comment 5 for bug 1525706

I believe the problem is that all world immovables are checked, instead of just the ones on the map:
http://bazaar.launchpad.net/~widelands-dev/widelands/trunk/view/head:/src/logic/map.cc#L2067

If someone told be how to call this function for the whole map, I could try to fix it:
 uint32_t find_immovables
  (const Area<FCoords>,
   std::vector<ImmovableFound> * list,
   const FindImmovable & = find_immovable_always_true());