zebra: Add link parameters support to Zebra

* zebra/interface.c:
   - Add new link-params CLI commands
   - Add new functions to set/get link parameters for interface
* zebra/redistribute.[c,h]: Add new function to propagate link parameters
  to routing daemon (essentially OSPFD and ISISD) for Traffic Engineering.
* zebra/redistribute_null.c: Add new function
  zebra_interface_parameters_update()
* zebra/zserv.[c,h]: Add new functions to send link parameters

Signed-off-by: Olivier Dugeon <olivier.dugeon@orange.com>
diff --git a/zebra/zserv.h b/zebra/zserv.h
index 413cd6a..9d65998 100644
--- a/zebra/zserv.h
+++ b/zebra/zserv.h
@@ -108,6 +108,8 @@
 extern int zsend_router_id_update (struct zserv *, struct prefix *,
                                    vrf_id_t);
 
+extern int zsend_interface_link_params (struct zserv *, struct interface *);
+
 extern pid_t pid;
 
 #endif /* _ZEBRA_ZEBRA_H */