pgsql: Add a function pg_get_keywords() to let clients find out the set

Log Message:
-----------
Add a function pg_get_keywords() to let clients find out the set of keywords
known to the SQL parser. Dave Page

Modified Files:
--------------
pgsql/doc/src/sgml:
func.sgml (r1.437 -> r1.438)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/func.sgml?r1=1.437&r2=1.438)
pgsql/src/backend/parser:
keywords.c (r1.197 -> r1.198)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/parser/keywords.c?r1=1.197&r2=1.198)
pgsql/src/backend/utils/adt:
misc.c (r1.62 -> r1.63)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/utils/adt/misc.c?r1=1.62&r2=1.63)
pgsql/src/include/catalog:
catversion.h (r1.464 -> r1.465)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/include/catalog/catversion.h?r1=1.464&r2=1.465)
pg_proc.h (r1.503 -> r1.504)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/include/catalog/pg_proc.h?r1=1.503&r2=1.504)
pgsql/src/include/parser:
keywords.h (r1.24 -> r1.25)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/include/parser/keywords.h?r1=1.24&r2=1.25)
pgsql/src/include/utils:
builtins.h (r1.317 -> r1.318)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/include/utils/builtins.h?r1=1.317&r2=1.318)