Utility for cgo
https://github.com/golang/proposal/blob/master/design/12416-cgo-pointers.md
In go 1.6, cgo argument can't be passed Go pointer.
var s string
C.pass_pointer(pointer.Save(&s))
v := *(pointer.Restore(C.get_from_pointer()).(*string))
go get github.com/mattn/go-pointer
MIT
Yasuhiro Matsumoto (a.k.a mattn)
