fixed windows picking renderer for core profile by disabling blending and

enabling depth test

RenderPickingPlugin.cc

@@ -164,12 +164,12 @@ void RenderPickingPlugin::render(ACG::GLState* _glState, Viewer::ViewerPropertie
   {
     ACG::GLState::disable(GL_LIGHTING);
   }
-  ACG::GLState::enable(GL_BLEND);
   glClear(GL_DEPTH_BUFFER_BIT);
 
   // do the picking
   _glState->pick_init (true);
   ACG::SceneGraph::PickAction action(*_glState, pickRendererMode_, _properties.drawMode());
+  _glState->enable(GL_DEPTH_TEST);
   ACG::SceneGraph::traverse_multipass( PluginFunctions::getSceneGraphRootNode() , action,*_glState);
 
   if(_glState->compatibilityProfile())