Merge pull request zendframework/zendframework#2135 from Thinkscape/h…

…otfix/callable-not-callback

Change all 'callback' typehints to 'callable'

src/Di.php

@@ -392,7 +392,7 @@ protected function createInstanceViaConstructor($class, $params, $alias = null)
     /**
      * Get an object instance from the defined callback
      *
-     * @param  callback                           $callback
+     * @param  callable                           $callback
      * @param  array                              $params
      * @param  string                             $alias
      * @return object