In pg_upgrade, remove use of whichCluster, and just pass old/new cluster

Bruce Momjian <bruce@momjian.us>

Commit: 6e6bee987ff4b6d650eec9f20fd477269d95e295
Author: Bruce Momjian <bruce@momjian.us>
Date: 2011-01-01T17:06:36Z
Releases: 9.1.0
In pg_upgrade, remove use of whichCluster, and just pass old/new cluster
pointers, which simplifies the code.  This was not possible in 9.0 because
everything was in a single nested struct, but is possible now.

Per suggestion from Tom.

Files