* Added DetourCrowdPhysics.h/cpp to enable use of bullet physics, based on
this discussion: https://groups.google.com/forum/?fromgroups=#!searchin/recastnavigation/physics/recastnavigation/NzK6yGUXqXs/6mT6P-Nu89sJ

* Refactored autotools to create DetourCrowdPhysics.la and related.