Log Message:
-----------
Prevent CLUSTER from decreasing a relation's relfrozenxid. Bug
introduced in rewrite to make CLUSTER MVCC-safe.
Modified Files:
--------------
pgsql/src/backend/commands:
cluster.c (r1.167 -> r1.168)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/commands/cluster.c?r1=1.167&r2=1.168)