Changes to LLVM to support deoptimization.

Added a magic exception value (-1) and a handler to transition
to the interpreter. This is currently untested.

Change-Id: I2f53135e7505c54355ecf7c579897f68bbdcbda3
diff --git a/src/thread.h b/src/thread.h
index c63fddf..5e424c1 100644
--- a/src/thread.h
+++ b/src/thread.h
@@ -325,6 +325,10 @@
     managed_stack_.SetTopQuickFramePc(pc);
   }
 
+  void SetTopOfShadowStack(ShadowFrame* top) {
+    managed_stack_.SetTopShadowFrame(top);
+  }
+
   bool HasManagedStack() const {
     return managed_stack_.GetTopQuickFrame() != NULL || managed_stack_.GetTopShadowFrame() != NULL;
   }