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_2_STABLE

Modified Files:
--------------
    pgsql/src/backend/commands:
        dbcommands.c (r1.187.2.3 -> r1.187.2.4)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/commands/dbcommands.c?r1=1.187.2.3&r2=1.187.2.4)
        user.c (r1.174 -> r1.174.2.1)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/commands/user.c?r1=1.174&r2=1.174.2.1)
    pgsql/src/backend/utils/misc:
        guc.c (r1.360.2.7 -> r1.360.2.8)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/utils/misc/guc.c?r1=1.360.2.7&r2=1.360.2.8)
    pgsql/src/include/utils:
        guc.h (r1.76.2.1 -> r1.76.2.2)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/include/utils/guc.h?r1=1.76.2.1&r2=1.76.2.2)