gui: preserve order of gui_print vs gui_msg

- rename __gui_print to internal_gui_print (__* is reserved for compiler)
- translate outstanding messages in internal_gui_print
- add locking because background thread could print while we render
- minor cleanup

Change-Id: Ib687d2cfb4763ad08ad4d4b76daf5b129d61d2e2
diff --git a/gui/objects.hpp b/gui/objects.hpp
index 28ed29c..630cf71 100644
--- a/gui/objects.hpp
+++ b/gui/objects.hpp
@@ -746,7 +746,9 @@
 	virtual size_t GetItemCount();
 	virtual void RenderItem(size_t itemindex, int yPos, bool selected);
 	virtual void NotifySelect(size_t item_selected);
+
 	static void Translate_Now();
+	static void Clear_For_Retranslation();
 protected:
 	enum SlideoutState
 	{