need clarifications on net/radix.c usage

[Luigi Rizzo]

Hi,
i am revising the code in net/radix.c and there are a few
things that are not completely clear to me and I would like
to understand and possibly fix.

I know that this code has been untouched in 15 years so it
probably reflects old requirements or design ideas that have
changed since then.

Initial list of things:

- struct radix_node_head has a number of fields that are never used
  (rnh_addpkt and friends, rnh_addrsize, rnh_pktsize)
  Unless there are objections I'd like to remove the unused fields.

- there are some static variables in radix.c (max_keylen, mask_rnhead,
  the freelist, the allzero and allone masks, 'last_zeroed' in a function)
  which would probably deserve becoming members of radix_node_head,
  last not least for correctness of operation -- some of those fields
  are read-write, but there are now multiple instances of radix_node_head
  running under different locks.
     Again, if there are no objections, I'd like to move those variables
  into radix_node_head.

cheers
luigi