add standby information

[a320321wb]

in master
postgres=# select pg_is_in_recovery()::int;
pg_is_in_recovery

             0

(1 row)
in standby
postgres=# select pg_is_in_recovery()::int;
pg_is_in_recovery

            1

(1 row)

select pg_is_in_recovery()::int; is run on standby