std.range.iota enhancement: supporting more types (AKA issue 10762)

[Jakob Ovrum]

On Saturday, 28 December 2013 at 14:13:08 UTC, Francesco 
Cattoglio wrote:
> It's always the same "issue": you have to compute the last 
> element inside iota, you should never rely on the user giving 
> you ideal inputs.

Alright, so require division for bidirectionality when given a 
custom step. There's no reason division should be required for 
bidirectionality in the most common case of iota(start, end).