Add the possibility to control the storage mode of scalar value (by value or reference)
in order to avoid unecessary copies when using complex scalar types (e.g., a AutoDiffScalar)

Eigen/src/Core/Functors.h

diff --git a/Eigen/src/Core/Functors.h b/Eigen/src/Core/Functors.h
index cbaeb83..ef4485f 100644
--- a/Eigen/src/Core/Functors.h
+++ b/Eigen/src/Core/Functors.h
@@ -350,7 +350,7 @@
   EIGEN_STRONG_INLINE Scalar operator() (const Scalar& a) const { return a * m_other; }
   EIGEN_STRONG_INLINE const PacketScalar packetOp(const PacketScalar& a) const
   { return ei_pmul(a, ei_pset1(m_other)); }
-  const Scalar m_other;
+  const typename NumTraits<Scalar>::Nested m_other;
 private:
   ei_scalar_multiple_op& operator=(const ei_scalar_multiple_op&);
 };
@@ -364,7 +364,7 @@
   EIGEN_STRONG_INLINE ei_scalar_multiple2_op(const ei_scalar_multiple2_op& other) : m_other(other.m_other) { }
   EIGEN_STRONG_INLINE ei_scalar_multiple2_op(const Scalar2& other) : m_other(other) { }
   EIGEN_STRONG_INLINE result_type operator() (const Scalar1& a) const { return a * m_other; }
-  const Scalar2 m_other;
+  const typename NumTraits<Scalar2>::Nested m_other;
 };
 template<typename Scalar1,typename Scalar2>
 struct ei_functor_traits<ei_scalar_multiple2_op<Scalar1,Scalar2> >
@@ -393,7 +393,7 @@
   EIGEN_STRONG_INLINE ei_scalar_quotient1_impl(const ei_scalar_quotient1_impl& other) : m_other(other.m_other) { }
   EIGEN_STRONG_INLINE ei_scalar_quotient1_impl(const Scalar& other) : m_other(other) {}
   EIGEN_STRONG_INLINE Scalar operator() (const Scalar& a) const { return a / m_other; }
-  const Scalar m_other;
+  const typename NumTraits<Scalar>::Nested m_other;
 };
 template<typename Scalar>
 struct ei_functor_traits<ei_scalar_quotient1_impl<Scalar,false> >