pgsql: Report index name on CLUSTER failure.

Log Message:
-----------
Report index name on CLUSTER failure. Also, suggest ALTER TABLE
WITHOUT CLUSTER for cluster failure of a single table in a full db
cluster.

Modified Files:
--------------
pgsql/src/backend/commands:
cluster.c (r1.137 -> r1.138)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/commands/cluster.c.diff?r1=1.137&r2=1.138)
tablecmds.c (r1.156 -> r1.157)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/commands/tablecmds.c.diff?r1=1.156&r2=1.157)
pgsql/src/include/commands:
cluster.h (r1.27 -> r1.28)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/include/commands/cluster.h.diff?r1=1.27&r2=1.28)