add licence info

api/tess_version.h.in

@@ -1,3 +1,23 @@
+///////////////////////////////////////////////////////////////////////
+// File:        version.h
+// Description: Version information
+//
+// (C) Copyright 2018, Google 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.
+//
+///////////////////////////////////////////////////////////////////////
+
+#ifndef TESSERACT_API_VERSION_H_
+#define TESSERACT_API_VERSION_H_
+
 #define TESSERACT_MAJOR_VERSION @GENERIC_MAJOR_VERSION@
 #define TESSERACT_MINOR_VERSION @GENERIC_MINOR_VERSION@
 #define TESSERACT_MICRO_VERSION @GENERIC_MICRO_VERSION@
@@ -6,3 +26,5 @@
    TESSERACT_MINOR_VERSION << 8 | \
    TESSERACT_MICRO_VERSION)
 #define TESSERACT_VERSION_STR "@PACKAGE_VERSION@"
+
+#endif  // TESSERACT_API_VERSION_H_