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).

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