Log Message:
In amanda*, reduce default options.

Add an 'ndmp' option, disabled by default.
Disable kerberos option by default.

These two changes allow amanda to build again on OS X.  My belief,
posited on pkgsrc-users without contradiction, is that no pkgsrc users
use these features anyway.  Normal amanda usage these days is over ssh
(which gets one PFS).  NDMP is for direct dumping of NAS: usage is
probably rare and also in large installations where rebuilding is not
hard.

All in all, I thought it better for the pkgsrc/amanda universe to have
consistent options across platforms than to selectively disable on OS
X.