Add Handle/HandleScope and delete SirtRef.

Delete SirtRef and replaced it with Handle. Handles are value types
which wrap around StackReference*.

Renamed StackIndirectReferenceTable to HandleScope.

Added a scoped handle wrapper which wraps around an Object** and
restores it in its destructor.

Renamed Handle::get -> Get.

Bug: 8473721

Change-Id: Idbfebd4f35af629f0f43931b7c5184b334822c7a
diff --git a/runtime/fault_handler.h b/runtime/fault_handler.h
index ea2f7c8..97d3c2f 100644
--- a/runtime/fault_handler.h
+++ b/runtime/fault_handler.h
@@ -112,7 +112,7 @@
 };
 
 
-// Statically allocated so the the signal handler can get access to it.
+// Statically allocated so the the signal handler can Get access to it.
 extern FaultManager fault_manager;
 
 }       // namespace art