To shorten the list we need to run if filename trans rules exist for the type
of the given parent directory I put them in a hashtable.  Given the policy we
are expecting to use in Fedora this takes the worst case list run from about
5,000 entries to 17.
Signed-off-by: NEric Paris <eparis@redhat.com>
Reviewed-by: NJames Morris <jmorris@namei.org>