Hide LRO code under #ifdef INET/INET6 to allow NOIP kernel to compile.

While the code comments indicate that LRO is currently only supported
for IPv4/TCP, we'll still compile it in for IPv6.

MFC after:	3 days
Make net.add_addr_allfibs vnet-local.
Virtualize interface cloner for gif(4).  This fixes a panic when destroying
a vnet jail which has a gif(4) interface.
- Virtualize interface cloner for gre(4).  This fixes a panic when destroying
  a vnet jail which has a gre(4) interface.

- Make net.link.gre.max_nesting vnet-local.
Fix a bug which could make routed(8) daemon exit by sending a special RIP
query from a remote machine, and disable accepting it by default.  This
requests a routed(8) daemon to dump routing information base for debugging
purpose.  An -i flag to enable it has been added.