instanceOf now uses RTTI and checks its answer.

Next I'll just remove it, but this commit lets me
have something in history such that I can fall back to
check for bugs that might get introduced.

lout/identity.cc

@@ -99,7 +99,7 @@ void IdentifiableObject::registerName (const char *className, const std::type_in
  * \brief Returns, whether this class is an instance of the class, given by
  *    \em otherClassId, or of a sub class of this class.
  */
-bool IdentifiableObject::instanceOf (std::intptr_t otherClassId)
+bool IdentifiableObject::instanceOf_impl (std::intptr_t otherClassId)
 {
    if (otherClassId == -1)
       // Other class has not been registered yet, while it should have been,