request: add support for binary copy

[mmisiewicz]

When using psql to \copy a table with ulids, the copy fails as follows:

(74046) [local]:5432 mike@mike=#  \copy (select * from foo) to foo.bin with (format binary)
ERROR:  no binary output function available for type ulid

(table foo contains a column named id that is of type ulid.)

This is using the current tip of master. The request is to add a binary representation compatible with COPY.

[mmisiewicz]

Looks like this issue is a dupe of: #27