I'd say not. If people want `log` base 2 or 10, they should use the appropriate functions.

One potential numeric issue here is maintaining monotonicity. If we swap out libm `log` calls for `log2` calls for some inputs, we not only make the code more complicated, but also risk breaking monotonicity.

So -1 from me on the special casing.

I'd be very happy with exposing exp2 in the math library, but that's a separate issue.