Script file or eval code are not interactive session so keep Octave quiet. * libinterp/octave.cc: add a new static variable an_octave_program to keep track when this is called for an Octave program and not for an Octave interactive session. The main point of this patch is so that octave_startup_message() on octave_execute_interpreter() is not called. A continuation work from csets 6ba5f1ff041e and f3ac54ac2c6a which also aimed at doing this. The idea is to have an_octave_program inherit other features of a non-interactive session (such as being canceled by forcing an interactive session or not starting readline).

((nil .
      ((c-file-style . "gnu")
       (indent-tabs-mode . nil)
       (fill-column . 72)
       (eval . (when (and (buffer-file-name)
                          (string-match-p "\\.h\\'" (buffer-file-name))
                          (not (string-match-p "/gnulib/" (buffer-file-name))))
                 (c++-mode)
                 (c-set-style "gnu")))))
 (change-log-mode . ((indent-tabs-mode . t)))
 (makefile-mode . ((indent-tabs-mode . t))))