This is embarrassing, but the iterator returned by this method seems to
have always been wrong, ever since it was added back in 946954d3bf
(Added reverse iterator to wxVector<T>, 2008-09-16). Moreover, it was
also broken in its const_reverse_iterator counterpart where it was
copy-and-pasted in f7ef20685f (Add wxVector<>::const_reverse_iterator,
2013-05-08).
Finally fix this to return the correct value and add at least a simple
unit test check that this method behaves as expected.
5495389db5