[PATCH 0/2] Get flow key down into ipv4 datagram packet engine

The really nice part about this patch set is that it will subsequently
allow us to kill a lot of on-stack stuff.

Parts of what we pass around in the flow key is also passed around in
this "ipcm_cookie" object we use for datagram/raw/icmp packet
construction.

So now we can perform some minimizations on ipcm_cookie as a result.