Add Octave input request

[SylvainCorlay]

test_input_42 is not a valid mock input for GNU Octave, which causes the test failure.

The input string should be a valid Octave expression, like "hello" or 1, but just typing hello will trigger an error if the hello variable is not defined.

[SylvainCorlay]

A fix would be to change

let mock_input = "test_input_42";

into

let mock_input = "\"test_input_42\"";

but maybe a cleaner fix would be to use a language-dependent input string.

[SylvainCorlay]

It does not seem that we can merge over the Conformance Matrix check failing to post the comment on the PR:

It seems that the previous PR by Johan had the same test failing and you merged. It seems to be a permission issue with a GitHub token.