ADD: new track message, Entity class and Position class

libs/eigen/failtest/swap_1.cpp

@@ -0,0 +1,14 @@
+#include "../Eigen/Core"
+
+using namespace Eigen;
+
+int main()
+{
+  VectorXf a(10), b(10);
+#ifdef EIGEN_SHOULD_FAIL_TO_BUILD
+  const DenseBase<VectorXf> &ac(a);
+#else
+  DenseBase<VectorXf> &ac(a);
+#endif
+  b.swap(ac);
+}