ADD: new track message, Entity class and Position class

libs/eigen/failtest/ref_3.cpp

@@ -0,0 +1,15 @@
+#include "../Eigen/Core"
+
+using namespace Eigen;
+
+#ifdef EIGEN_SHOULD_FAIL_TO_BUILD
+void call_ref(Ref<VectorXf> a) { }
+#else
+void call_ref(const Ref<const VectorXf> &a) { }
+#endif
+
+int main()
+{
+  VectorXf a(10);
+  call_ref(a+a);
+}