Incorrect documentation for boost::geometry::traits::ring_type

[john.firebaugh@…]

http://www.boost.org/doc/libs/1_61_0/libs/geometry/doc/html/geometry/reference/concepts/concept_polygon.html states:

there must be a specialization of traits::ring_type defining the type of its exterior ring and interior rings as type

As far as I can tell, the specializations must actually be of traits::ring_mutable_type and traits::ring_const_type. There is no traits::ring_type template to specialize.

A similar issue exists with the documentation referring to traits::interior_type -- this should instead refer to traits::interior_mutable_type and traits::interior_const_type.