pgsql: Add ONLY support to LOCK and TRUNCATE.

Log Message:
-----------
Add ONLY support to LOCK and TRUNCATE. By default, these commands are now
recursive.

=> Note this incompatibility in the release notes.

Modified Files:
--------------
pgsql/doc/src/sgml/ref:
lock.sgml (r1.51 -> r1.52)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/ref/lock.sgml?r1=1.51&r2=1.52)
truncate.sgml (r1.31 -> r1.32)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/ref/truncate.sgml?r1=1.31&r2=1.32)
pgsql/src/backend/commands:
lockcmds.c (r1.20 -> r1.21)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/commands/lockcmds.c?r1=1.20&r2=1.21)
tablecmds.c (r1.276 -> r1.277)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/commands/tablecmds.c?r1=1.276&r2=1.277)
pgsql/src/backend/parser:
gram.y (r2.652 -> r2.653)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/parser/gram.y?r1=2.652&r2=2.653)
pgsql/src/test/regress/expected:
truncate.out (r1.18 -> r1.19)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/test/regress/expected/truncate.out?r1=1.18&r2=1.19)
pgsql/src/test/regress/sql:
truncate.sql (r1.7 -> r1.8)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/test/regress/sql/truncate.sql?r1=1.7&r2=1.8)