Prevent multiple inclusions of NativeTokenizer header

Added #pragma once on top of the file to prevent multiple inclusion.

Change-Id: I351ada48e16bf6bfe84b546da5581b1aa6bce03e
Signed-off-by: Sebastien Gonzalve <sebastien.gonzalve@intel.com>
diff --git a/utility/NaiveTokenizer.h b/utility/NaiveTokenizer.h
index 2558e37..67abc9a 100644
--- a/utility/NaiveTokenizer.h
+++ b/utility/NaiveTokenizer.h
@@ -28,6 +28,8 @@
  * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
+#pragma once
+
 class NaiveTokenizer {
 public:
     /** tokenize a space-separated string, handling quotes