Work around unstable matrix inversion in DUNE 2.[34]

The versions are missing the specialized code for inverting
a 3x3 matrix that makes the algorithms quite a bit more stable.
With this patch we fall back to using our own MatrixBlock that does
not suffer from this deficiency.

opm/autodiff/ParallelOverlappingILU0.hpp

@@ -238,14 +238,17 @@ public:
       \param n ILU fill in level (for testing). This does not work in parallel.
       \param w The relaxation factor.
     */
-    ParallelOverlappingILU0 (const Matrix& A, const int n, const field_type w )
+    template<class Matrix1>
+    ParallelOverlappingILU0 (const Matrix1& A, const int n, const field_type w )
         : lower_(),
           upper_(),
           inv_(),
           comm_(nullptr), w_(w),
           relaxation_( std::abs( w - 1.0 ) > 1e-15 )
     {
-        init( A, n );
+        // BlockMatrix is a Subclass of FieldMatrix that just adds
+        // methods. Therefore this cast should be safe.
+        init( reinterpret_cast<const Matrix&>(A), n );
     }
 
     /*! \brief Constructor.
@@ -254,7 +257,8 @@ public:
       \param A The matrix to operate on.
       \param w The relaxation factor.
     */
-    ParallelOverlappingILU0 (const Matrix& A, const field_type w)
+    template<class Matrix1>
+    ParallelOverlappingILU0 (const Matrix1& A, const field_type w)
         : ParallelOverlappingILU0( A, 0, w )
     {
     }
@@ -266,14 +270,17 @@ public:
       \param comm   communication object, e.g. Dune::OwnerOverlapCopyCommunication
       \param w      The relaxation factor.
     */
-    ParallelOverlappingILU0 (const Matrix& A, const ParallelInfo& comm, const field_type w)
+    template<class Matrix1>
+    ParallelOverlappingILU0 (const Matrix1& A, const ParallelInfo& comm, const field_type w)
         : lower_(),
           upper_(),
           inv_(),
           comm_(&comm), w_(w),
           relaxation_( std::abs( w - 1.0 ) > 1e-15 )
     {
-        init( A, 0 );
+        // BlockMatrix is a Subclass of FieldMatrix that just adds
+        // methods. Therefore this cast should be safe.
+        init( reinterpret_cast<const Matrix&>(A), 0 );
     }
 
     /*!