[m-rev.] for post-commit review: optimize contains/insert pairs in digraph.m

[Peter Wang]

On Wed, 01 Feb 2023 16:22:43 +1100 "Zoltan Somogyi" <zoltan.somogyi at runbox.com> wrote:
> Optimize contains/insert pairs in digraph.m ...
> 
> ... by replacing them with insert_new operations.
> 
> Delete redundant module qualifications.

That's fine.

Peter