BUG #15603: LibPQ doesn't like replication as a valid option

The following bug has been logged on the website:

Bug reference:      15603
Logged by:          James Sewell
Email address:      james.sewell@gmail.com
PostgreSQL version: 11.1
Operating system:   Linux
Description:

When I look at the LibPQ documentation I don't see replication (which I
*think* can be true or database) listed as a valid option.

I would expect that it would be listed here:

https://www.postgresql.org/docs/11/libpq-connect.html#LIBPQ-PARAMKEYWORDS

It *is* mentioned in passing here:

https://www.postgresql.org/docs/11/protocol-replication.html

And it obviously works!