use shortcut manager for the debug menu * main-window.cc (add_action): new function for adding actions to menus and setting Qt::ApplicationShortcut to the actions; (construct_debug_menu_item): do not set shortcuts but the slot here; (construct_debug_menu): update calls to construct_debug_menu_item; (set_global_shortcuts): set the shortcut for the actions and the settings key * main-window.h: new function add_action, changed paramters of construct_debug_menu_item * shortcut-manager.cc (do_init_data): init the shortcuts for the debug menus

Things to do before making a release:

  * Update the version number and release date in configure.ac.

  * Update the NEWS file.

  * Update the NEWS-<VERSION>.html, index.in, news.in, and download.in
    files for the web site.

  * Copy tarballs to ftp.gnu.org.

  * Post a release announcement to the help@octave.org and
    info-gnu@gnu.org lists.