DHCP support

[Marco Gerards]

Hi,

DHCP wasn't possible yet because of two reasons:

- The routing tabled need to be set up. Because of lacking routing
  interface this was not possible.

- The IP address of 0.0.0.0 was not valid.

I've added the RPCs so adding/deleting routes is possible now. If this
patch is committed support to glibc should be added.

To make the "0.0.0.0" IP address valid (which is required for DHCP,
see the RFC) I've removed a check. This check checked if the IP
address "0.0.0.0" was set and removed the current UP from pfinet. We
don't require this behavior because we can shutdown pfinet using
settrans. Can someone comment on this please? (and if possible on
savannah? :)).

Before a DHCP client is supported the client should be changed a
bit. Alfred started working on this, I also have some changes.

Please have a look at my patches on savannah for more details.

Thanks,
Marco

ps. I have a test program to make the routing table DHCP ready (using
these interfaces). If someone really wants it I can mail it to this
list.