[MRG] update sklearn.svm.bounds to use recent helpers

Here was some code with stale conventions. If it is useful code, perhaps it should be available in `linear_model` (and for alpha), not just in `svm`.
@jnothman I don't know, I don't understand the maths behind this function. However, in practice the datasets are most commonly inseparable, so I'd be surprised if this function is useless in these cases.