relfilenode.

I sent the CLUSTER patch a few days ago and I think it was missed.  I
append it again, this time including the regression test files.  For the
committer, please note that you have to cvs add the files as they don't
exist.  Maybe add to the parallel and serial schedules also, but I don't
know such stuff.

Alvaro Herrera (<alvherre[a]atentus.com>)