====================
- Every method with ``lonlat`` in its name now has an alias with ``lonlat``
replaced by ``radec``.
- The class ``_SingleSphericalPolygon`` has been renamed to
``SingleSphericalPolygon``. The former name has been retained as an alias.
- The from_lonlat (and from_radec) method is now available in
``SingleSphericalPolygon`` as well as ``SphericalPolygon``.
- The methods ``iter_polygons_flat`` have been renamed to to ``__iter__``. The
former name has been retained as an alias.