[RFC] Prune net.inet6.ip6.rr_prune?

[Garrett Cooper]

    While going through the tree trying to document all of our
net.inet6 sysctls, I noticed that net.inet6.ip6.rr_prune is defined,
but not actually used anywhere in the stack:

netinet6/ip6_var.h:VNET_DECLARE(int, ip6_rr_prune);  /* router
renumbering prefix
netinet6/ip6_var.h:#define   V_ip6_rr_prune                  VNET(ip6_rr_prune)
netinet6/in6_proto.c:VNET_DEFINE(int, ip6_rr_prune) = 5;     /* router
renumbering prefix
netinet6/in6_proto.c:SYSCTL_VNET_INT(_net_inet6_ip6, IPV6CTL_RR_PRUNE,
rr_prune, CTLFLAG_RW,
netinet6/in6_proto.c:        &VNET_NAME(ip6_rr_prune), 0,

    The knob was declared in r181803 and shuffled around a few times,
but isn't in use anywhere (either then or now).
    Should I send out a PR to remove it (or am I missing some context)?
Thanks,
-Garrett