Support priv/unpriv image extraction

Optionally add back privileged extraction which can be enabled with
LUET_PRIVILEGED_EXTRACT=true

Signed-off-by: Ettore Di Giacinto <mudler@sabayon.org>

vendor/github.com/hashicorp/go-immutable-radix/edges.go

@@ -0,0 +1,21 @@
+package iradix
+
+import "sort"
+
+type edges []edge
+
+func (e edges) Len() int {
+	return len(e)
+}
+
+func (e edges) Less(i, j int) bool {
+	return e[i].label < e[j].label
+}
+
+func (e edges) Swap(i, j int) {
+	e[i], e[j] = e[j], e[i]
+}
+
+func (e edges) Sort() {
+	sort.Sort(e)
+}