Core: Move the titlebar / statusbar abstraction to DolphinWX

The concept of a "title bar" / "status bar" shouldn't be a core concept,
so remove the Host_UpdateStatusBar function, and move the code handles
whether to update the status bar or titlebar into DolphinWX.

Source/Core/DolphinWX/MainNoGUI.cpp

@@ -102,8 +102,6 @@ bool Host_RendererHasFocus()
 
 void Host_ConnectWiimote(int wm_idx, bool connect) {}
 
-void Host_UpdateStatusBar(const std::string& text, int filed){}
-
 void Host_SysMessage(const char *fmt, ...)
 {
 	va_list list;