Sparse module:

* several fixes (transpose, matrix product, etc...)
 * Added a basic cholesky factorization
 * Added a low level hybrid dense/sparse vector class
   to help writing code involving intensive read/write
   in a fixed vector. It is currently used to implement
   the matrix product itself as well as in the Cholesky
   factorization.

Eigen/Sparse

@@ -13,6 +13,7 @@ namespace Eigen {
 #include "src/Sparse/SparseUtil.h"
 #include "src/Sparse/SparseMatrixBase.h"
 #include "src/Sparse/SparseArray.h"
+#include "src/Sparse/AmbiVector.h"
 #include "src/Sparse/SparseBlock.h"
 #include "src/Sparse/SparseMatrix.h"
 #include "src/Sparse/HashMatrix.h"
@@ -21,6 +22,7 @@ namespace Eigen {
 #include "src/Sparse/SparseSetter.h"
 #include "src/Sparse/SparseProduct.h"
 #include "src/Sparse/TriangularSolver.h"
+#include "src/Sparse/BasicSparseCholesky.h"
 
 } // namespace Eigen