Clean OSD messages code

Some OSD messages were displayed in RenderBase.cpp using global variables and some code duplicated
in OnScreeDisplay.cpp.
Now all messages are displayed using functions in the OSD namepace.

* OSDChoice and OSDTime global variables are gone
* All OSD logic is kept at the same place
* All messages are properly aligned
* Clean characters for all OSD messages

Original commit:

commit f0ec61c057
Author: Aestek <thib.gilles@gmail.com>
Date:   Sun Aug 7 16:08:41 2016 +0200

Source/Core/DolphinWX/Frame.h

@@ -337,6 +337,13 @@ private:
 
   bool InitControllers();
 
+  // OSD
+  void OSDPrintInternalResolution();
+  void OSDPrintAspectRatio();
+  void OSDPrintEFB();
+  void OSDPrintFog();
+  void OSDPrintEmulationSpeed();
+
   // Event table
   DECLARE_EVENT_TABLE();
 };