pg_cancel_backend by non-superuser

This patch would appear(?) to have languished:

https://commitfest.postgresql.org/action/patch_view?id=541

I'd really like to see it included.  In the last comments of the
review, there seem to be problems in *terminate* backend, but even
just pg_cancel_backend as non-superuser would be just a huge
improvement.  What are the things blocking non-superuser
pg_cancel_backend from being accepted?

-- 
fdr