Messages: add option to change size of message text

Include default size and localized setup.

TODO: localize for nederlands and slovak, current english only.

src/system/settings.h

@@ -683,6 +683,7 @@ struct SNeutrinoSettings
 		FONT_TYPE_MOVIEBROWSER_LIST,
 		FONT_TYPE_MOVIEBROWSER_INFO,
 		FONT_TYPE_SUBTITLES,
+		FONT_TYPE_MESSAGE_TEXT,
 		FONT_TYPE_COUNT
 	};