CppTools: Offer "override" and "final" as completion items

These are special identifiers and were thus not included in the 'add all
keywords' handling.

Change-Id: I7f65df5711193e945bfa955dcb70a6ab454606b5
Task-number: QTCREATORBUG-11341
Reviewed-by: Erik Verbruggen <erik.verbruggen@theqtcompany.com>
Reviewed-by: Eike Ziller <eike.ziller@theqtcompany.com>

src/plugins/cpptools/cppcompletion_test.cpp

@@ -168,6 +168,8 @@ bool isProbablyGlobalCompletion(const QStringList &list)
             + (T_FIRST_OBJC_AT_KEYWORD - T_FIRST_KEYWORD);
 
     return list.size() >= numberOfPrimitivesAndBasicKeywords
+        && list.contains(QLatin1String("override"))
+        && list.contains(QLatin1String("final"))
         && list.contains(QLatin1String("if"))
         && list.contains(QLatin1String("bool"));
 }