Misc message style and doc fixes.

doc/src/sgml/ref/pg_recvlogical.sgml

src/backend/replication/libpqwalreceiver/libpqwalreceiver.c

src/bin/pg_basebackup/pg_basebackup.c

src/bin/pg_basebackup/pg_recvlogical.c

src/bin/psql/command.c