Add internationalization hints.

src/prefs/GUIPrefs.cpp

@@ -198,6 +198,7 @@ void GUIPrefs::PopulateOrExchange(ShuttleGui & S)
                     wxT("/GUI/BlendThemes"),
                     true);
 #ifndef __WXMAC__
+      /* i18n-hint: RTL stands for 'Right to Left'  */
       S.TieCheckBox(_("Use mostly Left-to-Right layouts in RTL languages"),
          "/GUI/RtlWorkaround",
          true);