UPDATE: MPLS: lo(4) integration, refactoring routing

Compartements relating route installation / removal
refactored entirely.

struct mpls_ftn {
	struct rtentry	*ftn_ilm;
	struct llentry	*ftn_lle;
	struct ifaddr	*ftn_ifa;
	int	ftn_flags;
	struct sockaddr_ftn	ftn_dst;

	struct sockaddr_mpls	ftn_iseg;
	struct sockaddr_mpls	ftn_oseg;

	struct sockaddr	*ftn_fec;
	struct rtentry	*ftn_rt;
    struct ifnet	*ftn_ifp;
    struct sockaddr	*ftn_nh;
	struct sockaddr	*ftn_gw;
};

is derived from struct route{} and holds
MPLS route or is used by mpls_control()
or by mpls_rt_output_fib() for x-connect.

BTW, this commit contains flaws. Purpose
of this commit is to show only progress
on developement activities.