Making the function range_union_internal available to other extensions

[Esteban Zimanyi]

Dear all

In MobilityDB
https://github.com/MobilityDB/MobilityDB
we use extensively the range types.

Is there any possibility to make the function range_union_internal available to
use by other extensions ? Otherwise we need to copy/paste it verbatim. For
example lines 114-153 in
https://github.com/MobilityDB/MobilityDB/blob/develop/src/rangetypes_ext.c

Regards

Esteban