Big rewrite in the Sparse module: SparseMatrixBase no longer inherits MatrixBase.

That means a lot of features which were available for sparse matrices
via the dense (and super slow) implemention are no longer available.
All features which make sense for sparse matrices (aka can be implemented efficiently) will be
implemented soon, but don't expect to see an API as rich as for the dense path.
Other changes:
* no block(), row(), col() anymore.
* instead use .innerVector() to get a col or row vector of a matrix.
* .segment(), start(), end() will be back soon, not sure for block()
* faster cwise product

Eigen/src/Core/Transpose.h

@@ -63,8 +63,6 @@ template<typename MatrixType> class Transpose
 
     EIGEN_GENERIC_PUBLIC_INTERFACE(Transpose)
 
-    class InnerIterator;
-
     inline Transpose(const MatrixType& matrix) : m_matrix(matrix) {}
 
     EIGEN_INHERIT_ASSIGNMENT_OPERATORS(Transpose)
@@ -185,7 +183,7 @@ struct ei_inplace_transpose_selector<MatrixType,false> { // non square matrix
   *
   * In most cases it is probably better to simply use the transposed expression
   * of a matrix. However, when transposing the matrix data itself is really needed,
-  * then this "in-place" version is probably the right choice because it provides 
+  * then this "in-place" version is probably the right choice because it provides
   * the following additional features:
   *  - less error prone: doing the same operation with .transpose() requires special care:
   *    \code m.set(m.transpose().eval()); \endcode