pgsql-server: Use gettext_noop() to mark strings.

Log Message:
-----------
Use gettext_noop() to mark strings. errmsg() perform the
real gettext() later on, so it was called twice before.

Modified Files:
--------------
pgsql-server/src/backend/libpq:
auth.c (r1.115 -> r1.116)
(http://developer.postgresql.org/cvsweb.cgi/pgsql-server/src/backend/libpq/auth.c.diff?r1=1.115&r2=1.116)