Fix/disjoint

PR fixing Areal/Areal version by replacing `point_on_surface()` with `point_on_border()` and `within()` with `covered_by()` for backward compatibility (https://svn.boost.org/trac/boost/ticket/8310).

Related to https://github.com/boostorg/geometry/pull/159 and https://github.com/boostorg/geometry/pull/162.

Actually writing:
```
has_within = geometry::point_on_border(pt, range) && geometry::covered_by(pt, m_geometry);
```
is obviously wrong.
What I wanted to suggest is:
```
has_within ||= (geometry::point_on_border(pt, range) && geometry::covered_by(pt, m_geometry));
```
This way you avoid any geometric computations (`point_on_border` and `covered_by`) is `has_within` has already been set to `true`.