- remove Eval/EvalOMP (moving them to a disabled/ subdir in order

to preserve SVN history). They are made useless by the new
  ei_eval_unless_lazy.
- introduce a generic Eval member typedef so one can do e.g.
  T t; U u; Product<T, U>::Eval m; m = t*u;

disabled/class_Eval.cpp

@@ -0,0 +1,28 @@
+#include <Eigen/Core>
+USING_PART_OF_NAMESPACE_EIGEN
+using namespace std;
+
+template<typename Derived>
+const Eigen::Eval<Eigen::Transpose<Derived> >
+evaluatedTranspose(const MatrixBase<Derived>& m)
+{
+  return m.transpose().eval();
+}
+
+int main(int, char**)
+{
+  Matrix2f M = Matrix2f::random();
+  Matrix2f m;
+  m = M;
+  cout << "Here is the matrix m:" << endl << m << endl;
+  cout << "Now we want to replace m by its own transpose." << endl;
+  cout << "If we do m = m.transpose(), then m becomes:" << endl;
+  m = m.transpose();
+  cout << m << endl << "which is wrong!" << endl;
+  cout << "Now let us instead do m = evaluatedTranspose(m). Then m becomes" << endl;
+  m = M;
+  m = evaluatedTranspose(m);
+  cout << m << endl << "which is right." << endl;
+
+  return 0;
+}