DDMsgReader: For Synchronet >= 3.20, read external editor quote wrap setting from xtrn.ini (rather than xtrn.cnf)

DDMsgReader: For Synchronet >= 3.20, read external editor quote wrap setting from xtrn.ini (rather than xtrn.cnf). Also, there's a new user setting to toggle whether or not to use the scrollbar in the scrolling reader. Currently there is no alternate progress displayed if not using the scrollbar, but that is planned for a future update.