Added license info to demo.c

demo.c

+/*
+ * demo.c - Example use of the BS-SPEKE functions
+ *
+ * Author: Charles V. Wright <cvwright@futo.org>
+ * 
+ * Copyright (c) 2022 FUTO Holdings, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>