ALTER ROLE SET/RESET for multiple options

Hi all,

ALTER ROLE SET/RESET can set/reset only one GUC parameter per one SQL today.
So when we need to set/reset multiple GUC parameter to user, it would
be burdensome work.

I'd like propose feature makes ALTER ROLE SET/RESET can set/reset
multiple options like ALTER TABLE.
ALTER USER is as well.

For example,

postgres(1)=# CREATE USER hoge_user ;
CREATE ROLE
postgres(1)=# ALTER USER hoge_user SET (log_statement = ddl,
log_min_messages = notice, application_name = 'HOGE');
ALTER ROLE
postgres(1)=# SELECT * FROM pg_db_role_setting ;
setdatabase | setrole | setconfig
-------------+---------+-------------------------------------------------------------------
0 | 16384 |
{log_statement=ddl,log_min_messages=notice,application_name=HOGE}
(1 row)

postgres(1)=# ALTER USER hoge_user RESET (log_statement, log_min_messages);
ALTER ROLE
postgres(1)=# SELECT * FROM pg_db_role_setting ;
setdatabase | setrole | setconfig
-------------+---------+-------------------------
0 | 16384 | {application_name=HOGE}
(1 row)

Attached draft v1 patch.
Please give me feedback.

Regards,

--
Masahiko Sawada