Copy head (r256279) to stable/10 as part of the 10.0-RELEASE cycle.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

Fix 'make depend'.

Fix ip_divert handling of inet and inet6 and module building some more.

Properly sort the "carp" case in modules/Makefile after it was renamed.

Reported by: bde (most)
Reviewed by: bde
MFC after: 3 days

Add possibility to pass IPv6 packets to a divert(4) socket.

Submitted by: sem

Convert IPDIVERT into a loadable module. This makes use of the dynamic loadability
of protocols. The call to divert_packet() is done through a function pointer. All
semantics of IPDIVERT remain intact. If IPDIVERT is not loaded ipfw will refuse to
install divert rules and natd will complain about 'protocol not supported'. Once
it is loaded both will work and accept rules and open the divert socket. The module
can only be unloaded if no divert sockets are open. It does not close any divert
sockets when an unload is requested but will return EBUSY instead.