Enable use of custom XHR loader for TileVector sources

src/ol/tileloadfunction.js

@@ -1,4 +1,5 @@
 goog.provide('ol.TileLoadFunctionType');
+goog.provide('ol.TileVectorLoadFunctionType');
 
 
 /**
@@ -9,3 +10,13 @@ goog.provide('ol.TileLoadFunctionType');
  * @api
  */
 ol.TileLoadFunctionType;
+
+
+/**
+ * A function that is called with a tile url for the features to load and
+ * a callback that takes the loaded features as argument.
+ *
+ * @typedef {function(string, function(Array.<ol.Feature>))}
+ * @api
+ */
+ol.TileVectorLoadFunctionType;