Correct comment about how reference is selected in select_cluster.
Correct comment about how reference is selected in select_cluster.

As pointed out by Ruth Franklin, the code is correct but the comment
erroneously referred to the non-composite rather than original algorithm
(which is currently the only approach which generates the reference
directly from select_cluster).

hande-qmc/hande,hande-qmc/hande,ruthfranklin/hande,hande-qmc/hande,hande-qmc/hande,hande-qmc/hande