r17798: Beginnings of a standalone libaddns library released under

r17798: Beginnings of a standalone libaddns library released under
the LGPL.   Original code by Krishna Ganugapati <krishnag@centeris.com>.
Additional work by me.

It's still got some warts, but non-secure updates do
currently work.  There are at least four things left to
really clean up.

1. Change the memory management to use talloc() rather than
   malloc() and cleanup the leaks.
2. Fix the error code reporting (see initial changes to
   dnserr.h)
3. Fix the secure updates
4. Define a public interface in addns.h
5. Move the code in libads/dns.c into the libaddns/ directory
   (and under the LGPL).

A few notes:

* Enable the new code by compiling with --with-dnsupdate
* Also adds the command 'net ads dns register'
* Requires -luuid (included in the e2fsprogs-devel package).
* Has only been tested on Linux platforms so there may be portability
  issues.