Fixes to the native interface.

com.oracle.truffle.r.native/fficall/src/jni/Rembedded.c

@@ -645,17 +645,17 @@ SEXP R_getContextSrcRef(CTXT context) {
 int R_insideBrowser() {
 	JNIEnv *jniEnv = getEnv();
 	jmethodID methodID = checkGetMethodID(jniEnv, UpCallsRFFIClass, "R_insideBrowser", "()I", 0);
-    return (*jniEnv)->CallStaticIntMethod(jniEnv, UpCallsRFFIClass, methodID);
+    return (*jniEnv)->CallIntMethod(jniEnv, UpCallsRFFIObject, methodID);
 }
 
 int R_isGlobal(CTXT context) {
 	JNIEnv *jniEnv = getEnv();
 	jmethodID methodID = checkGetMethodID(jniEnv, UpCallsRFFIClass, "R_isGlobal", "(Ljava/lang/Object;)I", 0);
-    return (*jniEnv)->CallStaticIntMethod(jniEnv, UpCallsRFFIClass, methodID, context);
+    return (*jniEnv)->CallIntMethod(jniEnv, UpCallsRFFIObject, methodID, context);
 }
 
 int R_isEqual(void* x, void* y) {
 	JNIEnv *jniEnv = getEnv();
 	jmethodID methodID = checkGetMethodID(jniEnv, UpCallsRFFIClass, "R_isEqual", "(Ljava/lang/Object;Ljava/lang/Object;)I", 0);
-    return (*jniEnv)->CallStaticIntMethod(jniEnv, UpCallsRFFIClass, methodID, x, y);
+    return (*jniEnv)->CallIntMethod(jniEnv, UpCallsRFFIObject, methodID, x, y);
 }

com.oracle.truffle.r.native/fficall/src/jni/rffiutils.c

@@ -88,7 +88,7 @@ static jmp_buf* callErrorJmpBufTable[CALLDEPTH_STACK_SIZE];
 
 void init_utils(JNIEnv *env, jobject upCallsInstance) {
 	curenv = env;
-	UpCallsRFFIClass = (*env)->GetObjectClass(env, upCallsInstance);
+	UpCallsRFFIClass = (*env)->NewGlobalRef(env, (*env)->GetObjectClass(env, upCallsInstance));
 	UpCallsRFFIObject = (*env)->NewGlobalRef(env, upCallsInstance);
 	if (TRACE_ENABLED && traceFile == NULL) {
 		if (!isEmbedded) {