BUG: `^(::Float64, ::Union{Int, Float64})` incorrect for very large negative exponents

The floating point power function fails for a border case of integer argument:

```
julia> 2.0 ^ typemin(Int) # should be 0.0
0.5

julia> (-1.0) ^ typemin(Int) # should be 1.0
-1.0
```

The bug seems to be here: [Base.Math.pow_body(::Float64, ::Integer)](https://github.com/JuliaLang/julia/blob/e07c0f1ddbfc89ad1ac4dda7246d8ed5d0d57c19/base/math.jl#L1326)
