Make ol.geom.Circle support #intersectsExtent, with tests

src/ol/geom/circle.js

@@ -137,6 +137,29 @@ ol.geom.Circle.prototype.getType = function() {
 };
 
 
+/**
+ * @inheritDoc
+ * @api stable
+ */
+ol.geom.Circle.prototype.intersectsExtent = function(extent) {
+  var circleExtent = this.getExtent();
+  if (ol.extent.intersects(extent, circleExtent)) {
+    var center = this.getCenter();
+
+    if (extent[0] <= center[0] && extent[2] >= center[0]) {
+      return true;
+    }
+    if (extent[1] <= center[1] && extent[3] >= center[1]) {
+      return true;
+    }
+
+    return ol.extent.forEachCorner(extent, this.containsCoordinate, this);
+  }
+  return false;
+
+};
+
+
 /**
  * Set the center of the circle as {@link ol.Coordinate coordinate}.
  * @param {ol.Coordinate} center Center.