Make Reference::get follow const rules

Instead of having T* Reference::get() const, this change brings
const T* Reference::get() const and
      T* Reference::get()

Test: mma
Change-Id: I1c8834467acffd426c25aa9c0661c290a05d7a52
diff --git a/Interface.cpp b/Interface.cpp
index 7f33928..1ae6638 100644
--- a/Interface.cpp
+++ b/Interface.cpp
@@ -610,7 +610,7 @@
         // that would be caught in validate
         return nullptr;
     }
-    return static_cast<Interface*>(mSuperType.get());
+    return static_cast<const Interface*>(mSuperType.get());
 }
 
 std::vector<const Interface *> Interface::typeChain() const {