Move top-level typedefs to typedefs.js

With one exception, those directly in the `ol` namespace can be moved without problem.
Some left-over goog.requires are also removed.

src/ol/interaction/modifyinteraction.js

@@ -11,7 +11,6 @@ goog.require('ol.CollectionEventType');
 goog.require('ol.Feature');
 goog.require('ol.MapBrowserEvent.EventType');
 goog.require('ol.MapBrowserPointerEvent');
-goog.require('ol.Pixel');
 goog.require('ol.ViewHint');
 goog.require('ol.array');
 goog.require('ol.coordinate');