Numeric import update

Speed improvement for `double` and `float` versions of
```D
entropy
kullbackLeiblerDivergence
jensenShannonDivergence
```
Agreed. This is anti-pattern, but anti-pattern for anti-patterned std.math: std.math was created in two things in mind:
1. There is FPU stack.
2. FPU stack is fast.

In now days fast modern processors (or OS) can be without FPU stack. Furthermore modern x86 processors have slow FPU stack compered with XMM or YMM registers. If it will works 2 times faster we can use c log2 until new internals for std.math