use signal for octave_link::update_dbstop_marker * octave-qt-link.h (octave_qt_link): Derive from QObject. (octave_qt_link::update_dbstop_marker_signal): New signal. * libgui/src/module.mk (octave_gui_MOC): Include src/moc-octave-qt-link.cc in the list. * main-window.cc (main_window::construct): Connect octave_qt_link::update_dbstop_marker_signal to file_editor::handle_update_dbstop_marker_request. * octave-qt-link.cc (octave_qt_link::do_update_breakpoint): Emit signal instead of using event listener.