[PATCH 0/15]: More SKB list abstrations, this time frag lists

This adds some interface butter to skbuff.h so that we can (begin)
getting rid of explicit references to how frag lists of skbs are
managed.

I couldn't kill every such reference just yet.  Some things are
hard to abstract.

Looking forward I did some work to see what happens if we use
a list_head for the frag lists.  It doesn't work right unless
we clone all frag list SKBs during a pskb_copy() for example.

The single linked list we have no lets us just copy the head
skb->next pointer and bump SKB ref counts, so we may keep it
that way in the end.

Anyways, most of this is mechanical and will be pushed out to
net-next-2.6 in a few moments.