Create 'type' annotation for 'const' variables

From https://developers.google.com/closure/compiler/docs/js-for-compiler:
  "The type declaration and additional comment are optional. If you
  provide a type declaration, put the declaration on a separate line."

src/ol/sphere/normal.js

@@ -5,6 +5,7 @@ goog.require('ol.Sphere');
 
 /**
  * The normal sphere.
- * @const {ol.Sphere}
+ * @const
+ * @type {ol.Sphere}
  */
 ol.sphere.NORMAL = new ol.Sphere(6370997);