// Add.
func NewAddrRanges() AddrRanges {
	r := addrRanges{}
	r.init(testSysStat)
	return AddrRanges{r, true}
}

// MakeAddrRanges creates a new addrRanges populated with
// the ranges in a.
//
// The returned AddrRanges is immutable, so methods like
// Add will fail.
func MakeAddrRanges(a ...AddrRange) AddrRanges {
	// Methods that manipulate the backing store of addrRanges.ranges should