Several improvements in sparse module:

* add a LDL^T factorization with solver using code from T. Davis's LDL
  library (LPGL2.1+)
* various bug fixes in trianfular solver, matrix product, etc.
* improve cmake files for the supported libraries
* split the sparse unit test
* etc.

Eigen/src/Sparse/SparseProduct.h

@@ -162,6 +162,7 @@ struct ei_sparse_product_selector<Lhs,Rhs,ResultType,ColMajor,ColMajor,ColMajor>
       for (typename Rhs::InnerIterator rhsIt(rhs, j); rhsIt; ++rhsIt)
       {
         // FIXME should be written like this: tmp += rhsIt.value() * lhs.col(rhsIt.index())
+        tempVector.restart();
         Scalar x = rhsIt.value();
         for (typename Lhs::InnerIterator lhsIt(lhs, rhsIt.index()); lhsIt; ++lhsIt)
         {