route: Add support for ttl propagation in MPLS routes

Add support for RTA_TTL_PROPAGATE attribute on a per-route basis.
Used to enable/disable TTL propagation at LSP egress.

Signed-off-by: David Ahern <dsahern@gmail.com>
diff --git a/libnl-route-3.sym b/libnl-route-3.sym
index bb2d658..4382775 100644
--- a/libnl-route-3.sym
+++ b/libnl-route-3.sym
@@ -1057,4 +1057,6 @@
 	rtnl_route_nh_get_newdst;
 	rtnl_route_nh_set_via;
 	rtnl_route_nh_get_via;
+	rtnl_route_set_ttl_propagate;
+	rtnl_route_get_ttl_propagate;
 } libnl_3_2_29;