Add ol.extent.forEachCorner
Add ol.geom.flat.segments.forEach
Add ol.geom.flat.contains.linearRingContainsExtent
Add ol.geom.flat.intersectsextent

Includes functions for testing if an extent and a geometry intersect.
Add ol.geom.Polygon#intersectsExtent
Add ol.geom.MultiPolygon#intersectsExtent
Add a box feature selection example