First commit. This project is not completely finished (the list_mkeys,

First commit.  This project is not completely finished (the list_mkeys,
purge_mkeys, sync_stash and update_princ_encryption still need to be
written) so the purpose of this commit is to allow early review of the
addition of support for > 1 master key and the "active" master keylist.
This commit does not include any changes required to sync this level of
the branch with the current level of the trunk.  That will follow this
commit.

git-svn-id: svn://anonsvn.mit.edu/krb5/branches/mkey_migrate@21721 dc483132-0cff-0310-8789-dd5450dbe970