sm::scale autoscale (and compute_scaling_from_data) behaviour if inf/NaN in input

[sebsjames]

Right now, if there's an inf in your input then

sc.transform (input, output);

will induce an autoscale (as it should) which then finds the params 0, 0 for the scaling.

This is confusing if you don't expect or know that there are infs in your input.