RE: Adding a '--clean-publisher-objects' option to 'pg_createsubscriber' utility.

Dear Peter,

Thanks for posting the patch. Largely it seems OK.

One comment:
I feel most of the word "remove" can be changed to "dropped", in pg_createsubscriber.c
and 040_pg_createsubscriber.pl. E.g.,

```
# Confirm the physical replication slot has been removed
$result = $node_p->safe_psql($db1,
    "SELECT count(*) FROM pg_replication_slots WHERE slot_name = '$slotname'"
);
is($result, qq(0),
    'the physical replication slot used as primary_slot_name has been removed'
);
```

And

```
    /* Remove failover replication slots if they exist on subscriber */
    drop_failover_replication_slots(dbinfos.dbinfo);
```


Best regards,
Hayato Kuroda
FUJITSU LIMITED