fix headers

use recommended headers and remove unused headers

java/jni/ZT_jniutils.cpp

@@ -21,7 +21,7 @@
 #include "ZT_jniarray.h"
 
 #include <string>
-#include <assert.h>
+#include <cassert>
 
 #include <arpa/inet.h>
 #include <netinet/in.h>

java/jni/ZT_jniutils.h

@@ -18,7 +18,7 @@
  
 #ifndef ZT_jniutils_h_
 #define ZT_jniutils_h_
-#include <stdio.h>
+
 #include <jni.h>
 #include <ZeroTierOne.h>
 

java/jni/com_zerotierone_sdk_Node.cpp

@@ -34,8 +34,8 @@
 
 #include <map>
 #include <string>
-#include <assert.h>
-#include <string.h>
+#include <cassert>
+#include <cstring>
 
 // global static JNI Lookup Object
 JniLookup lookup;