* sparse LU: add extraction of L,U,P, and Q, as well as determinant

for both backends.
* extended a bit the sparse unit tests

Eigen/src/Sparse/SparseMatrix.h

@@ -189,6 +189,10 @@ class SparseMatrix
         m_outerSize = outerSize;
       }
     }
+    void resizeNonZeros(int size)
+    {
+      m_data.resize(size);
+    }
 
     inline SparseMatrix()
       : m_outerSize(0), m_innerSize(0), m_outerIndex(0)