Added virtual destructor to reader and writer classes in order to avoid compiler warnings.

git-svn-id: http://www.openmesh.org/svnrepo/OpenMesh/trunk@84 fdac6126-5c0c-442c-9429-916003d36597

Core/IO/writer/PLYWriter.hh

@@ -73,6 +73,9 @@ public:
 
   _PLYWriter_();
 
+  /// Destructor
+  virtual ~_PLYWriter_() {};
+
   std::string get_description() const { return "PLY polygon file format"; }
   std::string get_extensions() const  { return "ply"; }