[master] Update client code to RFC7550

[master] Update client code to RFC7550

Update the v6 client code to handle getting
IA_NAs and IA_PDs in the same request better.

Squashed commit of the following:

commit ad1bf23100eba541c26c6c26fc2c5c9dc57dd674
Author: Shawn Routhier <sar@isc.org>
Date:   Mon Nov 16 23:08:13 2015 -0800

    [rt40190] Use dhc6_check_status for addresses and prefixes

commit 4cb1d499342e68c5c93b7e8dac71c9adbd737846
Author: Shawn Routhier <sar@isc.org>
Date:   Mon Nov 16 22:02:05 2015 -0800

    [rt40190] Correct the tests for a status code in the client

    Some of the tests for the NoAddrs or NoPrefix codes in the
    were incorrect, checking for a return of not success instead
    of success.

commit 41ad9ea4438c0f64b95ec7afeac38afd2f3b36cb
Author: Shawn Routhier <sar@isc.org>
Date:   Fri Nov 13 21:04:55 2015 -0800

    [rt40190] Update site.h to have the correct default

commit cb720dac6670e1a6cc19b22550506ded4093abef
Author: Shawn Routhier <sar@isc.org>
Date:   Fri Nov 13 21:03:38 2015 -0800

    [rt40190] update per second set of review comments

    Mostly this is a set of updates to the documentation.
    The only code change is to add a backwards compatibility
    option in includes/site.h for people who want the old weightings
    for the client lease scoring.

commit 269a5324b950062380b4e3988f56593dc21d05d9
Author: Thomas Markwalder <tmark@isc.org>
Date:   Thu Nov 12 09:00:36 2015 -0500

    [40190] Fixed another typo

commit 7da158497cd9236c30dfdce2b115818d1954839f
Author: Thomas Markwalder <tmark@isc.org>
Date:   Thu Nov 12 07:29:33 2015 -0500

    [40190] Minor cosmetics in dhc6.c

commit a010737de36e5ad2f46bb11f471ac66ccbc856aa
Author: Shawn Routhier <sar@isc.org>
Date:   Sat Nov 7 00:05:20 2015 -0800

    [rt40190] Update the use of the minimum score

    Update the use of the minimum score to use #defines instead
    of 150.  This corrects it for the current values and allows
    us to change the values if we include a backwards compatibility
    option.

commit b078575da08c06a75a49110273bf42e24d03c08a
Author: Shawn Routhier <sar@isc.org>
Date:   Fri Nov 6 21:55:05 2015 -0800

    [rt40190] Updates per review comments

    Update several comments to be more informative

    The code changes are mostly to fold all the two
    bare_ia routines together.

commit 248c498d45db5533f992fb6eb30ee6c3c399ee81
Author: Shawn Routhier <sar@isc.org>
Date:   Tue Oct 20 02:06:45 2015 -0700

    [rt40190] Fix up some typos

commit ba074eff2e82af0cfd25428e7f38bccd5fef7241
Author: Shawn Routhier <sar@isc.org>
Date:   Tue Oct 20 01:28:34 2015 -0700

    [rt40190] Patch for client side of 7550

    Finish up the code to handle multiple PDs and NAs
    in a single request, this includes updating the
    command line to add the -R option to require the
    requested IAs rather than accept the best advertised
    offer.

commit 5bb4368b8410e3c7bcdc28fdf4ae5572df04d03b
Author: Shawn Routhier <sar@isc.org>
Date:   Thu Oct 15 09:50:14 2015 -0700

    [rt40190] checkpoint my work

    The basic code is working there are still some issues with how
    corner cases get handled that I need to resolve

commit 4c0dba90fcd71c85fca3612aa5083fa11645f8f6
Author: Shawn Routhier <sar@isc.org>
Date:   Sun Oct 11 19:23:53 2015 -0700

    [rt40190] Some changes for rfc7550, to be updated

    This is being checked in so I can look at other tickets
    but I plan to re-arrange the code a fair amount.