CPlusPlus: Add more usage tags

To be used in subsequent patches.

Change-Id: Id7140aa39bb2adba343cc12b0273c90f3c12abeb
Reviewed-by: Christian Stenger <christian.stenger@qt.io>

src/libs/cplusplus/FindUsages.h

@@ -22,6 +22,8 @@ public:
         Read = 1 << 1,
         Write = 1 << 2,
         WritableRef = 1 << 3,
+        Override = 1 << 4,
+        MocInvokable = 1 << 5,
     };
     using Tags = QFlags<Tag>;