Added virtual destructors to calm compiler.

[[Imported from SVN: r2304]]

grid/common/virtualrefinement.cc

@@ -215,6 +215,10 @@ namespace Dune {
     typedef typename Refinement::CoordVector CoordVector;
 
     virtual CoordVector coords() const = 0;
+
+    virtual ~VirtualRefinementSubEntityIteratorBackSpecial()
+    {}
+
   };
 
   // The iterator backend for elements
@@ -227,6 +231,10 @@ namespace Dune {
     typedef typename Refinement::IndexVector IndexVector;
 
     virtual IndexVector vertexIndices() const = 0;
+
+    virtual ~VirtualRefinementSubEntityIteratorBackSpecial()
+    {}
+
   };
 
   // The iterator backend common stuff

grid/common/virtualrefinement.hh

@@ -327,6 +327,11 @@ namespace Dune {
     ElementIterator eBegin(int level) const;
     //! Get an ElementIterator
     ElementIterator eEnd(int level) const;
+
+    //! Destructor
+    virtual ~VirtualRefinement()
+    {}
+
   protected:
     virtual VertexIteratorBack *vBeginBack(int level) const = 0;
     virtual VertexIteratorBack *vEndBack(int level) const = 0;