make the majority of the callbacks stateless and add some status to a testcase

[cleverca22]

This change is

[iphydf]

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Reviewed 12 of 14 files at r1, 2 of 2 files at r2.
Review status: all files reviewed at latest revision, 1 unresolved discussion.

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auto_tests/tox_test.c, line 662 [r1] (raw file):

        tox_iterate(tox1, &to_compare);
        tox_iterate(tox2, &to_compare);
        tox_iterate(tox3, &packet_number);

Note to other reviewers: this is incorrect (but safe, it has the same type as to_compare) in theory. In practice, it works. Let's not focus on test code quality right now though.

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Comments from Reviewable

[JFreegman]

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Review status: all files reviewed at latest revision, 1 unresolved discussion, some commit checks failed.

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Comments from Reviewable

[JFreegman]

Reviewed 12 of 14 files at r1, 2 of 2 files at r2.
Review status: all files reviewed at latest revision, 1 unresolved discussion, some commit checks failed.

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Comments from Reviewable

[nurupo]

Reviewed 12 of 14 files at r1, 2 of 2 files at r2.
Review status: all files reviewed at latest revision, 2 unresolved discussions, some commit checks failed.

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auto_tests/tox_test.c, line 925 [r2] (raw file):

        if (counter != last_count) {
            printf("got to %d\n", counter);

Shouldn't that be %u instead?

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Comments from Reviewable

[GrayHatter]

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Reviewed 12 of 14 files at r1, 2 of 2 files at r2.
Review status: all files reviewed at latest revision, 2 unresolved discussions, some commit checks failed.

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Comments from Reviewable

[nurupo]

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Reviewed 2 of 2 files at r3.
Review status: all files reviewed at latest revision, 2 unresolved discussions.

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Comments from Reviewable