In-place "bang" versions of functions.

This works great. Because I do not need the arrays after calculations, I added in-place "bang" versions of the functions. This keeps allocations down.

```
julia> using Accelerate

julia> X = rand(1000000);

julia> @time Y = Accelerate.log(X);
elapsed time: 0.006102273 seconds (8013904 bytes allocated)

julia> @time Accelerate.log!(X);
elapsed time: 0.006830005 seconds (36072 bytes allocated)

julia> X == Y
true
```