Start adding implementations for runtime-provided native methods.

The library can't do everything...

Change-Id: Ib808c00570c7214aeb2ca058b1a66cacbeb372f1
diff --git a/src/runtime.h b/src/runtime.h
index 198bfeb..2717843 100644
--- a/src/runtime.h
+++ b/src/runtime.h
@@ -75,6 +75,8 @@
   // Attaches the current native thread to the runtime.
   bool AttachCurrentThread(const char* name, JNIEnv** jni_env, bool as_daemon);
 
+  void CallExitHook(jint status);
+
   // Detaches the current native thread from the runtime.
   bool DetachCurrentThread();