Re: array_cat anycompatible change is breaking xversion upgrade tests

I wrote:
> I think the most plausible response is to add this aggregate to the filter
> logic that already exists in the xversion tests. Perhaps we could
> alternatively change this test case so that it relies on some other
> polymorphic function, but I'm not quite sure what a good candidate
> would be.

After looking at the commit that added array_cat_accum() (65d9aedb1),
I decided that it's fine to replace this aggregate with one using another
anyarray function, such as array_larger(). The point of that test is just
to show that the array argument can be array-of-record, so we don't need
the operation to be array_cat() specifically. So I propose the attached
patches to un-break the xversion tests.

I'll hold off pushing this till after this week's wraps, though.

regards, tom lane