Add rows, cols enum to SingleNonZeroColumnMatrix.

dune/matrix-vector/singlenonzerocolumnmatrix.hh

@@ -46,6 +46,8 @@ class SingleNonZeroColumnMatrix
     };
 
 public:
+    enum { rows = ROWS, cols = COLS};
+
     typedef RowProxy row_type;
     typedef row_type const_row_reference;
     typedef typename std::size_t size_type;