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.

Tags:
----
REL8_3_STABLE

Modified Files:
--------------
pgsql/src/backend/commands:
dbcommands.c (r1.204.2.4 -> r1.204.2.5)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/commands/dbcommands.c?r1=1.204.2.4&r2=1.204.2.5)
user.c (r1.178 -> r1.178.2.1)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/commands/user.c?r1=1.178&r2=1.178.2.1)
pgsql/src/backend/utils/misc:
guc.c (r1.432.2.7 -> r1.432.2.8)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/utils/misc/guc.c?r1=1.432.2.7&r2=1.432.2.8)
pgsql/src/include/utils:
guc.h (r1.90 -> r1.90.2.1)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/include/utils/guc.h?r1=1.90&r2=1.90.2.1)