adding partitioned tables to publications

One cannot currently add partitioned tables to a publication.

create table p (a int, b int) partition by hash (a);
create table p1 partition of p for values with (modulus 3, remainder 0);
create table p2 partition of p for values with (modulus 3, remainder 1);
create table p3 partition of p for values with (modulus 3, remainder 2);

create publication publish_p for table p;
ERROR:  "p" is a partitioned table
DETAIL:  Adding partitioned tables to publications is not supported.
HINT:  You can add the table partitions individually.

One can do this instead:

create publication publish_p1 for table p1;
create publication publish_p2 for table p2;
create publication publish_p3 for table p3;

but maybe that's too much code to maintain for users.

I propose that we make this command:

create publication publish_p for table p;

automatically add all the partitions to the publication.  Also, any
future partitions should also be automatically added to the
publication.  So, publishing a partitioned table automatically
publishes all of its existing and future partitions.  Attached patch
implements that.

What doesn't change with this patch is that the partitions on the
subscription side still have to match one-to-one with the partitions
on the publication side, because the changes are still replicated as
being made to the individual partitions, not as the changes to the
root partitioned table.  It might be useful to implement that
functionality on the publication side, because it allows users to
define the replication target any way they need to, but this patch
doesn't implement that.

Thanks,
Amit