Add keyctl binary, which can be used to add fscrypt support to ext4 and
other filesystems that support it.

Signed-off-by: Rosen Penev <rosenp@gmail.com>

This reverts commit 41f2036afe.

Signed-off-by: Hannu Nyman <hannu.nyman@iki.fi>

Added Kerberos dependency as it's required now.

Signed-off-by: Rosen Penev <rosenp@gmail.com>

This is based on earlier work by Tobias Waldvogel.

Signed-off-by: W. Michael Petullo <mike@flyn.org>