[m-rev.] for post-commit review: output more readable inst defns

[Julien Fischer]

On Sat, 30 Oct 2021, Zoltan Somogyi wrote:

> Output more readable ":- inst" definitions.
> 
> compiler/parse_tree_out.m:
>     Do not wrap inst names in extra parentheses unnecessarily.
>
>     Use
>
>         :- inst i
>             --->    f1(i11, ..., i1N)
>             ;       f2(ii1, ..., i2N).
>
>     syntax if possible instead of the more cluttered general syntax
>
>         :- inst i == bound(f1(...) ; f2(...)).
>
>     when possible.
> 
> compiler/parse_tree_out_term.m:
>     Export a predicate for use by parse_tree_out.m.

That's fine.

Julien.