call encap_init.
call encap_init.

XXX in "options INET" case, we need to do it in in_proto.c.
we need to call it only once (it if not harmful to call it multiple times,
though).

MarginC/kame,MarginC/kame,MarginC/kame,MarginC/kame,MarginC/kame,MarginC/kame,MarginC/kame