vty: use install_lib_element() and install_lib_element_ve()

See https://lists.osmocom.org/pipermail/openbsc/2020-October/013278.html.

Change-Id: I5c0a1efc21a5cc085b701be24dbcca1aaae15ee6
Depends: I8baf31ace93c536421893c2aa4e3d9d298dcbcc6
Related: SYS#4937
diff --git a/src/iu_client_vty.c b/src/iu_client_vty.c
index a99facd..7388468 100644
--- a/src/iu_client_vty.c
+++ b/src/iu_client_vty.c
@@ -111,11 +111,11 @@
 {
 	g_rab_assign_addr_enc = rab_assign_addr_enc;
 
-	install_element(iu_parent_node, &cfg_iu_rab_assign_addr_enc_cmd);
+	install_lib_element(iu_parent_node, &cfg_iu_rab_assign_addr_enc_cmd);
 
 	/* Technically, these are global ASN.1 settings and not necessarily limited to the Iu interface.
 	 * Practically, only Iu users will use ASN.1 in Osmocom programs -- at least so far. So it is
 	 * easiest to have these commands under 'iu'. */
-	install_element(iu_parent_node, &cfg_iu_asn1_debug_cmd);
-	install_element(iu_parent_node, &cfg_iu_asn1_xer_print_cmd);
+	install_lib_element(iu_parent_node, &cfg_iu_asn1_debug_cmd);
+	install_lib_element(iu_parent_node, &cfg_iu_asn1_xer_print_cmd);
 }