pgsql: Prevent ALTER USER f RESET ALL from removing the settings that

Log Message:
-----------
Prevent ALTER USER f RESET ALL from removing the settings that were put there
by a superuser -- "ALTER USER f RESET setting" already disallows removing such a
setting.

Apply the same treatment to ALTER DATABASE d RESET ALL when run by a database
owner that's not superuser.

Modified Files:
--------------
pgsql/doc/src/sgml:
catalogs.sgml (r2.223 -> r2.224)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/catalogs.sgml?r1=2.223&r2=2.224)
pgsql/src/backend/catalog:
pg_db_role_setting.c (r1.3 -> r1.4)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/catalog/pg_db_role_setting.c?r1=1.3&r2=1.4)
pgsql/src/backend/utils/misc:
guc.c (r1.544 -> r1.545)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/utils/misc/guc.c?r1=1.544&r2=1.545)
pgsql/src/include/utils:
guc.h (r1.112 -> r1.113)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/include/utils/guc.h?r1=1.112&r2=1.113)