Pull up following revision(s) (requested by roy in ticket #131):

sys/netinet6/nd6.c: revision 1.260

inet6: nd6_free assumes all routers are processed by kernel RA

This hasn't been the case for a long time if you're a dhcpcd
user with a default config. As such, it's possible for the default
IPv6 router as set by dhcpcd could be erroneously gc'ed by nd6_free.

This reduces the scope of the ND6_WLOCK taken as well as fixing an
issue where we write to ln->ln_state without a lock being held.

(martin)