fix: correct iterator in map range on binary values (#644)

* fix: correct iterator in map range on binary values

The map range iterator was not initialized correctly for values
originating from runtime.

Fixes #641.

* test: deterministic output for map28.go

_test/map28.go

@@ -0,0 +1,21 @@
+package main
+
+import (
+	"net/url"
+)
+
+func main() {
+	value1 := url.Values{}
+
+	value1.Set("first", "v1")
+	value1.Set("second", "v2")
+
+	l := 0
+	for k, v := range value1 {
+		l += len(k) + len(v)
+	}
+	println(l)
+}
+
+// Output:
+// 13

interp/cfg.go

@@ -89,6 +89,8 @@ func (interp *Interpreter) cfg(root *node, pkgID string) ([]*node, error) {
 						switch typ.Kind() {
 						case reflect.Map:
 							n.anc.gen = rangeMap
+							ityp := &itype{cat: valueT, rtype: reflect.TypeOf((*reflect.MapIter)(nil))}
+							sc.add(ityp)
 							ktyp = &itype{cat: valueT, rtype: typ.Key()}
 							vtyp = &itype{cat: valueT, rtype: typ.Elem()}
 						case reflect.String: