* revert the previous interface change in solveTriangular (pointer vs reference)

* remove the cast operators in the Geometry module: they are replaced by constructors
  and new operator= in Matrix
* extended the operations supported by Rotation2D
* rewrite in solveTriangular:
  - merge the Upper and Lower specializations
  - big optimization of the path for row-major triangular matrices

Eigen/src/Geometry/Quaternion.h

@@ -118,6 +118,7 @@ public:
 
   /** Constructs and initializes a quaternion from the angle-axis \a aa */
   explicit inline Quaternion(const AngleAxisType& aa) { *this = aa; }
+
   /** Constructs and initializes a quaternion from either:
     *  - a rotation matrix expression,
     *  - a 4D vector expression representing quaternion coefficients.
@@ -131,9 +132,6 @@ public:
   template<typename Derived>
   Quaternion& operator=(const MatrixBase<Derived>& m);
 
-  /** Automatic conversion to a rotation matrix. */
-  operator Matrix3 () const { return toRotationMatrix(); }
-
   /** \returns a quaternion representing an identity rotation
     * \sa MatrixBase::Identity()
     */
@@ -426,4 +424,29 @@ struct ei_quaternion_assign_impl<Other,4,1>
   }
 };
 
+/** \geometry_module
+  *
+  * Constructs a 3x3 rotation matrix from the quaternion \a q
+  *
+  * \sa Matrix(const AngleAxis&)
+  */
+template<typename _Scalar, int _Rows, int _Cols, int _MaxRows, int _MaxCols, unsigned int _Flags>
+Matrix<_Scalar, _Rows, _Cols, _MaxRows, _MaxCols, _Flags>::Matrix(const Quaternion<Scalar>& q)
+{
+  EIGEN_STATIC_ASSERT_MATRIX_SPECIFIC_SIZE(Matrix,3,3);
+  *this = q.toRotationMatrix();
+}
+
+/** \geometry_module
+  *
+  * Set a 3x3 rotation matrix from the quaternion \a q
+  */
+template<typename _Scalar, int _Rows, int _Cols, int _MaxRows, int _MaxCols, unsigned int _Flags>
+Matrix<_Scalar, _Rows, _Cols, _MaxRows, _MaxCols, _Flags>&
+Matrix<_Scalar, _Rows, _Cols, _MaxRows, _MaxCols, _Flags>::operator=(const Quaternion<Scalar>& q)
+{
+  EIGEN_STATIC_ASSERT_MATRIX_SPECIFIC_SIZE(Matrix,3,3);
+  return *this = q.toRotationMatrix();
+}
+
 #endif // EIGEN_QUATERNION_H