Slight innacuracy in Log2 implementation in math/math.hpp (loss of precision?)

[emilydolson]

When using the implementation of log2 in the standard cmath library, log2(0.166667) returns -2.58496. Using Empirical's Log2 function Log2(0.166667), however, returns -2.58532. Seems like it's some sort of minor loss of precision error, but could still lead to substantial inaccuracies over time. I assume this is due to some sort of loss of precision error somewhere, but I can't see where.