BOSTON - The Old North Church, where two lanterns were hung to signal Paul Revere that the British were coming, will receive federal grant money for a fix-up under a change in government policy on church and state. Old North is still an active Episcopal church, and up to now, historically significant structures that were also used for religious purposes have been ineligible for federal historic preservation grants because of concerns about the separation of church and state. But Interior Secretary Gale Norton said Tuesday that under a new policy, all nationally significant historic structures can get grants.