Added option to allow verification of objects on the stack.

Currently it's defined out by VERIFY_OBJECT_ENABLED. Also made various
fixes to allow heap object verification to work again.

(cherry picked from commit d4983495782be8d54c9c1f0266dc52395b947724)

Change-Id: Icd625e1e0dc240c0ad1d10e2c58c7d5d63fec030
diff --git a/src/scoped_jni_thread_state.h b/src/scoped_jni_thread_state.h
index 2db04fc..552f5ed 100644
--- a/src/scoped_jni_thread_state.h
+++ b/src/scoped_jni_thread_state.h
@@ -29,6 +29,7 @@
       : env_(reinterpret_cast<JNIEnvExt*>(env)) {
     self_ = ThreadForEnv(env);
     old_thread_state_ = self_->SetState(Thread::kRunnable);
+    self_->VerifyStack();
   }
 
   ~ScopedJniThreadState() {