syscall: should to be migrated to use golang.org/x/sys

[LionNatsu]

Go has deprecated package syscall since 1.4. I think we should use the golang.org/x/sys repository.

See https://golang.org/pkg/syscall/#pkg-overview

[songgao]

Is there anything in golang.org/x/sys that would benefit this library? syscall is in standard library, thus has backward compatibility guarantees.

I'm not against migrating per se; I guess I'm just not sure about future paths of the two packages.

[LionNatsu]

@songgao I think the answer is yes. Stability and even compatibility and every bug fix. It has been frozen since 1.4 that means no one line changes since that, but the system interface changes.

A problems list from Go: https://golang.org/s/go1.4-syscall