pgsql: Use plurals (TABLES, FUNCTIONS, etc) in ALTER DEFAULT PRIVILEGES.

Log Message:
-----------
Use plurals (TABLES, FUNCTIONS, etc) in ALTER DEFAULT PRIVILEGES. We have
the keywords as a consequence of the GRANT ALL patch, so we might as well
use them and make the ALTER commands read more naturally.

Modified Files:
--------------
pgsql/doc/src/sgml/ref:
alter_default_privileges.sgml (r1.1 -> r1.2)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/ref/alter_default_privileges.sgml?r1=1.1&r2=1.2)
pgsql/src/backend/parser:
gram.y (r2.684 -> r2.685)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/parser/gram.y?r1=2.684&r2=2.685)
pgsql/src/bin/pg_dump:
dumputils.c (r1.50 -> r1.51)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/bin/pg_dump/dumputils.c?r1=1.50&r2=1.51)
pg_dump.c (r1.550 -> r1.551)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/bin/pg_dump/pg_dump.c?r1=1.550&r2=1.551)
pgsql/src/test/regress/expected:
privileges.out (r1.49 -> r1.50)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/test/regress/expected/privileges.out?r1=1.49&r2=1.50)
pgsql/src/test/regress/sql:
privileges.sql (r1.28 -> r1.29)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/test/regress/sql/privileges.sql?r1=1.28&r2=1.29)