Fix typos in comments

dune/istl/preconditioners.hh

@@ -923,7 +923,7 @@ namespace Dune {
     /**
      * \brief constructor
      *
-     * The constructor copies the matrix A and computes its ILU decomposition.
+     * The constructor copies the matrix A and computes its ILDL decomposition.
      *
      * \param[in]  A      matrix to operate on
      * \param[in]  relax  relaxation factor

dune/istl/superlu.hh

@@ -255,7 +255,7 @@ namespace Dune
    *
    * SuperLU supports single and double precision floating point and complex
    * numbers. Unfortunately these cannot be used at the same time.
-   * Therfore users must set SUPERLU_NTYPE (0: float, 1: double,
+   * Therefore users must set SUPERLU_NTYPE (0: float, 1: double,
    * 2: std::complex<float>, 3: std::complex<double>)
    * if the numeric type should be different from double.
    */