FIX verbosity of the mds

Now, the verbose option doesn't need to be strictly equal to 2 to print out
the stress at each iteration.
MAINT: unreachable code removed from BernoulliNB

The deleted code was unreachable. The previous call to check_arrays
ensures that X and y have consistent first dimensions.
BUG SVMlight loader should check whether n_features is big enough

scipy.sparse won't complain when it gets a dimensionality that is
too large, causing crashes in estimators.

Fixes #1630.
MAINT: use stable blas getter API