Optimizing: Reduce memory usage of HInstructions.

Pack narrow fields and flags into a single 32-bit field.

Change-Id: Ib2f7abf987caee0339018d21f0d498f8db63542d
diff --git a/runtime/primitive.h b/runtime/primitive.h
index ca42c47..2454a21 100644
--- a/runtime/primitive.h
+++ b/runtime/primitive.h
@@ -46,6 +46,7 @@
     kPrimFloat,
     kPrimDouble,
     kPrimVoid,
+    kPrimLast = kPrimVoid
   };
 
   static Type GetType(char type) {