[m-rev.] for post-commit review: always compute self-import FIM langs

[Zoltan Somogyi]

For review by anyone. I am mostly seeking feedback about
whether parse_tree_module_src should have TWO fields
for self-import FIM languages: those languages for which
the current module needs a self-import FIM in the interface
section, and one likewise for the implementation section.
My take is: yes, it should.

Zoltan.
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