dialog boxes with Qt widgets * dialog.h, dialog.cc: New files. * libgui/src/module.mk: Update file lists. * main-window.h, main-window.ccmain_window::connect_uiwidget_links, main_window::handle_create_dialog, main_window::handle_create_listview, main_window::handle_create_inputlayout): New functions. (main_window::construct): Call connect_uiwidget_links. * octave-link.h, octave-link.cc (octave_link::message_dialog, octave_link::do_message_dialog, octave_link::list_dialog, octave_link::do_list_dialog, octave_link::input_dialog, octave_link::do_input_dialog): New functions. * octave-qt-link.h, octave-qt-link.cc (octave_qt_link::message_dialog, octave_qt_link::do_message_dialog, octave_qt_link::list_dialog, octave_qt_link::do_list_dialog, octave_qt_link::input_dialog, octave_qt_link::do_input_dialog, make_qstring_list): New functions. * octave-link.cc (F__octave_link_edit_file__): Call flush_octave_stdout before running the edit file action. (F__octave_link_message_dialog__, F__octave_link_list_dialog__, __octave_link_input_dialog__): New functions. * errordlg.m, helpdlg.m, inputdlg.m, listdlg.m, msgbox.m, warndlg.m: New demos adapted from dlgtest.m * dlgtest.m: Delete. * scripts/java/module.mk: Remove it from the list of files. * inputdlg.m: Try __octave_link_input_dialog__ first. Only try java method if JAVA feature is available. * listdlg.m: Likwise, for __octave_link_list_dialog__. * private/message_dialog.m: Likewise, for __octave_link_message_dialog__.