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/renderer/canvas/canvaslayerrenderer.js

@@ -2,7 +2,6 @@ goog.provide('ol.renderer.canvas.Layer');
 
 goog.require('goog.asserts');
 goog.require('goog.vec.Mat4');
-goog.require('ol.Pixel');
 goog.require('ol.extent');
 goog.require('ol.layer.Layer');
 goog.require('ol.render.Event');