vty: Add functions to access index and node

It is easier to call these two functions from bindings than
wrapping the vty structure and figuring out the alignment of
the enum on all different ABIs.
diff --git a/src/vty/vty.c b/src/vty/vty.c
index ff17abf..5c5a908 100644
--- a/src/vty/vty.c
+++ b/src/vty/vty.c
@@ -248,6 +248,15 @@
 	return 0;
 }
 
+void *vty_current_index(struct vty *vty)
+{
+	return vty->index;
+}
+int vty_current_node(struct vty *vty)
+{
+	return vty->node;
+}
+
 int vty_config_lock(struct vty *vty)
 {
 	if (vty_config == 0) {