Misc. bugfixes. route(8) and netmpls/mpls_rmx.c.

Handling of gateway in rt_addrinfo{} by route(8) and netmpls/mpls_rmx.c
changed. Segements for x-connect are encoded by sockaddr_mpls{} maps to
sockaddr_ftn{}, where in-seg is stored by

 (a) satosmpls(dst)->smpls_label = ...

and out-seg by

 (b) satosftn(dst)->sftn_label = ...