ADD: new track message, Entity class and Position class

libs/eigen/failtest/sparse_ref_2.cpp

@@ -0,0 +1,15 @@
+#include "../Eigen/Sparse"
+
+using namespace Eigen;
+
+void call_ref(Ref<SparseMatrix<float> > a) { }
+
+int main()
+{
+  SparseMatrix<float> A(10,10);
+#ifdef EIGEN_SHOULD_FAIL_TO_BUILD
+  call_ref(A.row(3));
+#else
+  call_ref(A.col(3));
+#endif
+}