kernel: Use NULL for pointers.
network.subr - move get_if_var here
add load_kld to rc.subr

Obtained-from: FreeBSD
network.subr - use get_if_var extensively
ifconfig - use correct name after cloning

 * When running something like 'ifconfig vlan create vlandev foo vlan
   99', the vlan would be created correctly, but SIOCSETVLAN would be
   called on 'vlan' instead of the newly created vlan device.

 * Work around this by updating ifr_name from name (which is updated by
   the clone function) after doing the actual clone callback.
rc.conf - Add support for FreeBSD-style vlan conf

Obtained-from: FreeBSD
Revert "add load_kld to rc.subr"

This reverts commit 9b9814ddce54234e4b231ecb33b1de509a0a9bd5.

We don't really need load_kld, since ifconfig loads if_vlan on its own.