Implement java.lang.SecurityManager native methods

[lucasbaizer]

Native method: java/lang/SecurityManager.getClassContext()[Ljava/lang/Class;
Native method: java/lang/SecurityManager.currentClassLoader0()Ljava/lang/ClassLoader;
Native method: java/lang/SecurityManager.classDepth(Ljava/lang/String;)I
Native method: java/lang/SecurityManager.classLoaderDepth0()I
Native method: java/lang/SecurityManager.currentLoadedClass0()Ljava/lang/Class;