avoid pointer escape

Author: trend-amikai-chuang

iter.go

@@ -1,8 +1,8 @@
 package roaring
 
 func Values(b *Bitmap) func(func(uint32) bool) {
-	it := b.Iterator()
 	return func(yield func(uint32) bool) {
+		it := b.Iterator()
 		for it.HasNext() {
 			if !yield(it.Next()) {
 				return
@@ -12,8 +12,8 @@ func Values(b *Bitmap) func(func(uint32) bool) {
 }
 
 func Backward(b *Bitmap) func(func(uint32) bool) {
-	it := b.ReverseIterator()
 	return func(yield func(uint32) bool) {
+		it := b.ReverseIterator()
 		for it.HasNext() {
 			if !yield(it.Next()) {
 				return