Added PosixFile.symlink() and readLink().

src/main/cpp/generic.cpp

@@ -17,5 +17,5 @@ void mark_failed_with_code(JNIEnv *env, const char* message, int error_code, job
 
 JNIEXPORT jint JNICALL
 Java_net_rubygrapefruit_platform_internal_jni_NativeLibraryFunctions_getVersion(JNIEnv *env, jclass target) {
-    return 6;
+    return 7;
 }