Replace Handle with Local depending on Node.js version

Use newly introduced macros like SWIGV8_VALUE to use v8::Handle or
v8::Local depending on the selected Node.js version where possible.

Examples/test-suite/native_directive.i

@@ -53,7 +53,7 @@ extern "C" JNIEXPORT jint JNICALL Java_native_1directive_native_1directiveJNI_Co
 
 static SwigV8ReturnValue JavaScript_alpha_count(const SwigV8Arguments &args) {
   SWIGV8_HANDLESCOPE();
-  v8::Handle<v8::Value> jsresult;
+  SWIGV8_VALUE jsresult;
   char *arg1 = (char *)0;
   int res1;
   char *buf1 = 0;