It hadn't occurred to me that I should ask the release management team about adding a new function to libpq this late in the cycle.
Please do note that the message type used in the new routine is currenly unused and uncovered -- see line 4660 here: https://coverage.postgresql.org/src/backend/tcop/postgres.c.gcov.html -- Álvaro Herrera Valdivia, Chile "I'm impressed how quickly you are fixing this obscure issue. I came from MS SQL and it would be hard for me to put into words how much of a better job you all are doing on [PostgreSQL]." Steve Midgley, http://archives.postgresql.org/pgsql-sql/2008-08/msg00000.php
