[m-rev.] for post-commit review: construct initial module_and_imports directly

[Julien Fischer]

On Sat, 20 Apr 2019, Zoltan Somogyi wrote:

> For post-commit review by anyone.
>
> I would like everyone to try out the updated compiler on their Mercury
> code bases, and report the results: were the sanity checks added
> by this diff triggered, or not?

One of them (at least) is being triggered:

    Uncaught Mercury exception:
    Software Error: predicate
    `parse_tree.modules.grab_imported_modules_augment'/10: Unexpected: bad IntItems
    Stack dump not available in this grade.

I'll extract a test case for this one.

Julien.