[m-rev.] for review: Fix reverse implication goals.

[Julien Fischer]

On Thu, 28 Oct 2021, Peter Wang wrote:

> compiler/parse_goal.m:
>    Fix typo: A <= B was parsed as B => B.
>
> tests/hard_coded/Mmakefile:
> tests/hard_coded/implication.exp:
> tests/hard_coded/implication.m:
>    Add test case.
>

That's fine.

Julien.