[m-rev.] for review: convert mode analysis to use var_tables

[Julien Fischer]

On Mon, 2 May 2022, Zoltan Somogyi wrote:

>> The rest looks fine.
>
> Thanks. Please have a look at the diff for the tests,
> and say whether I can commit.

I suggest adding a comment to the test case saying that using disjoint
variables is important, other than that, it looks fine.

Julien.