Corrected wrong docstring in helper function ss
TST: sparse: mark dok matrix tests as knownfail with python 2.4 for 0.10.x.  See #1559.

It looked like PR-229 had fixed this issue by regenerating SWIG wrappers with a
newer version of SWIG (something we didn't understand), but a reported failure
from 0.11.0rc1 shows that this is not the case.  Therefore committing this to
master.  First submitted as PR-237.
DOC: fix cluster.vq.whiten docstring.

Output shows values with std(ddof=1), while numpy has used ddof=0 for a number
of years already.