TE: MPLS: route(8) and netmpls/mpls_rmx.c

Applied changes reduced code complexity dramatically.
	MPLS related code sections in switch statemant in newroute()
targeting route(8). And changes in netmpls/mpls_rmx.c.
    In any case dst denotes fec, gateway denotes segment. But
due to rt_addrinfo{} Service Primitive (SPI) in any case

  dst denotes Forward Equivalence Class (FEC)

further

  (a) RTF_POP, gateway denotes in-segment,
  (b) RTF_SWAP, gateway denotes in-segment

and finally

  (c) RTF_PUSH, gateway denotes out-segment

but

  ifaaddr denotes out-segment if and only if (iff)
  RTF_SWAP was defined implicitely.

Syntax of route(8) follows

  (a) route [add|delete] -pop MPLS_LABEL
  (b) route [add|delete] -push MPLS_LABEL
  (c) route [add|delete] -swap MPLS_LABEL -mpls MPLS_LABEL

Sometimes you see the forest for the trees!!! :-)

Next tasks:
-----------

  o Review of netmpls/mpls.c due to distinguishment
    between same labels in different label spaces.
    Meaning interface vs. radix trie.
  o Implementation of doublepush, stacking caused by
    external event from userland.
  o Assignement of reserved labels.