odhpc6c: status code support in reply

odhpc6c: status code support in reply

The patch implements support for status code handling in
reply messages as described in RFC3313 paragraph 18.1.8.
The client will
*log the status codes returned by the client
*send a request if no binding status code is returned for
a given IA
*send further renew/rebind if the IA was not present in
the reply
*terminate message exchange when no prefix/no address
status code is returned in reponse to a request
*terminate message exchange when unspec fail status code
is returned
*calculate t1/t2/t3 when all IA's have been processed and
based on recorded t1/t2/valid timer values per IA

Without this patch I have seen issues with request messages
send without any IA_PD/IA_NA and t1/t2/t3 timer values which
were not correct. These changes have been tested intensive
against an ISC DHCPv6 server

Signed-off-by: Hans Dedecker <hans.dedecker@gmail.com>