Use `roundeven` instead of `rint` for `round(x)`
The `llvm.rint` intrinsic is sensitive to the floating-point
environment, so determined enough users can change the definition
of `round(x, RoundNearest)` to not be rount to even.
```
julia> round(2.5, RoundNearest)
2.0
julia> Base.Rounding.setrounding_raw(Float64, Base.Rounding.to_fenv(RoundUp))
julia> round(2.5, RoundNearest)
3.0
julia> round_even(x::Float64) = ccall("llvm.roundeven.f64", llvmcall, Float64, (Float64,), x)
round_even (generic function with 1 method)
julia> round_even(2.5)
2.0
```
