[m-rev.] for review: Add hash table lookup predicates.

[Zoltan Somogyi]

On Thu,  1 Dec 2022 13:12:28 +1100, Peter Wang <novalazy at gmail.com> wrote:
> library/hash_table.m:
>     Add lookup predicate.
> 
> library/version_hash_table.m:
>     Add lookup predicate.
> 
>     Use higher-order field type with insts; delete inst casts.
> 
>     Use predicates instead of functions in a couple of places.
> 
> NEWS:
>     Announce additions.

Both this and the previous diff on version_array.lookup
are fine.

Zoltan.