    A pull-down menu appears when you move the mouse to the top of the scrn.  Menus
    are created with MenuPush(), MenuFilePush(), MenuNew() or MenuFile() and
    assigned to Fs->cur_menu.  The format is:

    File
    {
      Open(,'O');
      Save(,'S');
      Exit(,CH_SHIFT_ESC);
    }
    Edit {
      Cut(,,SC_DELETE|SCF_SHIFT);
      Paste(,,SC_INS|SCF_SHIFT);
    }
    Misc {
      Opt1(MSG_CMD,M_OPTION1);
      Opt2(MSG_CMD,M_OPTION2);
    }
    Help
    {
      Help(,'?');
      About(,'/');
    }

    The first arg is the msg code and it is optional with the default being
    MSG_KEY_DOWN_UP.  The second arg is the msg arg1 value which is ASCII of the key
    in the case of MSG_KEY_DOWN.  The third arg is the msg arg2 value which is the
    scan_code of the key in the case of MSG_KEY_DOWN.

    Press <CTRL-SHIFT-l> and "Insert ASCII/ScanCode".

    See ::/Demo/PullDownMenu.HC.