Cleanup headers

Change-Id: I9124366b2000cad54966fb6936bb4691bbf115a3
diff --git a/native/jni/src/char_utils.cpp b/native/jni/src/char_utils.cpp
index 9d2bc85..88803cb 100644
--- a/native/jni/src/char_utils.cpp
+++ b/native/jni/src/char_utils.cpp
@@ -14,7 +14,7 @@
  * limitations under the License.
  */
 
-#include <stdlib.h>
+#include <cstdlib>
 
 namespace latinime {