ENH: change base pattern "None" to "Hollow"

1. change base pattern "None" to "Hollow", and add an icon image
2. fix a bug of not initializing m_highest_overhang_layer
3. fix a bug where normal(auto) with Tree* styles won't generate any
   supports.
4. add popup message when selecting support material for interface.
5. draw connected loops when wall count is larger than 1

Change-Id: I7ea211d2971b25c65724bb10d0f6cf6e0b68c6a1
(cherry picked from commit 4c1ae7f937239fc3e1397ec2cb3b290d886bb0f0)

src/slic3r/GUI/GUI_App.hpp

@@ -589,7 +589,9 @@ private:
 
 DECLARE_APP(GUI_App)
 wxDECLARE_EVENT(EVT_CONNECT_LAN_MODE_PRINT, wxCommandEvent);
-} // GUI
+
+bool is_support_filament(int extruder_id);
+} // namespace GUI
 } // Slic3r
 
 #endif // slic3r_GUI_App_hpp_