func (iv interval16) runlen() int64 {
	return int64(iv.length) + 1
}
runlen returns the count of integers in the interval.
package roaring
import (
	"fmt"
	"sort"
	"unsafe"
)
type runContainer16 struct {
	iv   []interval16
	card int64
	myOpts searchOptions `msg:"-"`
}
type interval16 struct {
	start  uint16
	length uint16  
}
func newInterval16Range(start, last uint16) interval16 {
	if last < start {
		panic(fmt.Sprintf("last (%d) cannot be smaller than start (%d)", last, start))
	}
	return interval16{
		start,
		last - start,
	}
}