- In DHCPINFORM, allow for buggy clients that do not set ciaddr by

- In DHCPINFORM, allow for buggy clients that do not set ciaddr by
  using the IP source address from the IP header if ciaddr is zero.
- Fix some memory allocation botches.
- Use parameter request list option from scope if it is present and
  client didn't send one.
- Copy ciaddr from incoming packet to outgoing packet.
- Remember that we got the requested-address and server-identifier
  options in option state.
- Allow for RFC1541 clients that set ciaddr when REQUESTING by
  checking server-identifier option as well as ciaddr before
  unicasting.