bug#33870: 27.0.50; xref-goto-xref not configurable

[Juri Linkov]

> Example:
>
> Whoever designed the Lisp representation of a
> noncontiguous region trapped us the same way.
> By using a dotted pair of scalar values, that
> design pretty much precludes adding other info
> besides the start and end limits to a region
> segment.

You can override region-extract-function with your own
implementation that can support any shape you want.