Smack: Add smkfstransmute mount option

Smack: Add smkfstransmute mount option

Suppliment the smkfsroot mount option with another, smkfstransmute,
that does the same thing but also marks the root inode as
transmutting. This allows a freshly created filesystem to
be mounted with a transmutting heirarchy.

Targeted for git://git.gitorious.org/smack-next/kernel.git

(Upstream commit id: e830b39412ca2bbedd7508243f21c04d57ad543c)

Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>
Signed-off-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>