[m-rev.] for post-commit review: replace item-block-scanning code

[Julien Fischer]

On Sun, 11 Jul 2021, Zoltan Somogyi wrote:

> Replace some item-block-scanning code.
> 
> compiler/module_imports.m:
>     There were two data structures, the list of foreign include files
>     and the "contains foreign export" flag) that we used to to compute twice:
>     once using old code that scanned a list of item blocks, and once using
>     more modern data structures. Delete the old-code versions, since
>     we haven't had a discrepancy between the two versions for a long time.
>
>     For a third data structure, the set of fims (foreign_import_modules),
>     add the new code version, and add code to check for discrepancies.
> 
> compiler/item_util.m:
>     Delete the old code that used to compute the first two data structures.
> 
> compiler/prog_data_foreign.m:
>     Add a utility predicate for use by module_imports.m. Give some predicates
>     shorter names.
> 
> compiler/hlds_module.m:
>     Conform to the changes above.
> 
> compiler/make.dependencies.m:
>     Clarify a piece of code.

That's fine.

Julien.