The current macaddr datatype needs to be kept for some time by renaming
it without changing OID and use the newer one for further usage.
From the point of view of a driver maintainer... Npgsql looks up data types by their name - upon first connection to a database it queries pg_type and maps its internal data type handlers based on name. This allows it to avoid hardcoding data type OIDs in source code, and easily handle user-defined data types as well (enums, composites...). So a sudden rename of a datatype would definitely cause a problem. Of course it's possible to first check the server version and act accordingly but it seems to complicate things needlessly.
