trunk: add MLS constrains for ingress/egress permissions from Paul Moore.
    
    Add MLS constraints for several network related access controls including
    the new ingress/egress controls and the older Secmark controls.  Based on
    the following post to the SELinux Reference Policy mailing list:
    
     * http://oss.tresys.com/pipermail/refpolicy/2009-February/000579.html