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/heap.h b/src/heap.h
index be8c62a..7717871 100644
--- a/src/heap.h
+++ b/src/heap.h
@@ -243,6 +243,8 @@
 
   void VerifyObjectLocked(const Object *obj);
 
+  void VerifyHeapLocked();
+
   static void VerificationCallback(Object* obj, void* arg);
 
   Mutex* lock_;