no native dialogs to prevent hangs in KDE (patch #7948 by Andre da Costa Barros) * main-window.cc(handle_save_workspace_request,handle_load_workspace_request, browse_for_directory): open the dialogs as qt instead native dialogs * file-editor.cc(request_open_file): configure the file dialog not being native * file-editor-tab.cc(save_file_as): configure the file dialog not being native * files-Dock-widget.cc(popdownmenu_search_dir): search dir dialog not native