Include kernel stacks on non-ARM hardware.

Also explicitly say when we have no managed frames (so their absence
is clearly deliberate in those rare cases where it happens).

Change-Id: I5cd60235faad9297dcbeaa2aea62a101b8e20e89
diff --git a/src/thread.h b/src/thread.h
index c5695cf..8ff9dfb 100644
--- a/src/thread.h
+++ b/src/thread.h
@@ -484,6 +484,7 @@
 
   void DumpState(std::ostream& os) const;
   void DumpStack(std::ostream& os) const;
+  void DumpKernelStack(std::ostream& os) const;
   void DumpNativeStack(std::ostream& os) const;
 
   // Out-of-line conveniences for debugging in gdb.