added xnor cpu forward function
added xnor cpu forward function

hpi-xnor/BMXNet,hpi-xnor/BMXNet,hpi-xnor/BMXNet,hpi-xnor/BMXNet,hpi-xnor/BMXNet,hpi-xnor/BMXNet,hpi-xnor/BMXNet,hpi-xnor/BMXNet,hpi-xnor/BMXNet