Update with newer version of CLUSTER patch posted August 8.

Update with newer version of CLUSTER patch posted August 8.

> Looks like Alvaro got sideswiped by the system catalog indexing changes
> I made over the weekend.  It's a simple change, just reduce the whole
> mess to a "CatalogUpdateIndexes()" call.

I update two tuples, so I manually CatalogOpenIndexes() and
CatalogIndexInsert() two times, as per comments in
CatalogUpdateIndexes().

I also removed a couple of useless CommandCounterIncrement(), some
useless definitions in src/include/commands/cluster.h and useless
includes in src/backend/commands/cluster.c.  This version passes the
regression test I had made for previous versions.

Alvaro Herrera