Use free function hasDictionary()

This is a bug fix that fixes a framework unit test in DataFormats/FWLite.  In our ROOT6 code, unlike our ROOT 5 code, the constructor for TypeWithDict throws a fatal exception if the class in question does not have a dictionary.
Therefore, instead of invoking TypeWithDict(myTypeInfo).hasDictionary(), we must call the new free function hasDictionary(myTypeInfo) to check if the class has a dictionary.
This fix could, in principle, be made in the ROOT5 code as well, but that would involve some extra work.