0025133: TKOpenGl - Crash on closing a view containing presentations with capping

OpenGl_Element destruction and resource deallocation methods now accept
a pointer to OpenGl_Context instead of a handle to avoid double deletion
of the context.

samples/qt/VoxelDemo/src/VoxelClient_VisDrawer.cxx

@@ -42,7 +42,7 @@ public:
 
   void Render (const Handle(OpenGl_Workspace) &theWorkspace) const;
 
-  virtual void Release (const Handle(OpenGl_Context)& theContext)
+  virtual void Release (OpenGl_Context* theContext)
   {
     //
   }