Provide ol.RendererType structure through ol.renderer.Map

It was previously in ol.Map, but it could not be provided because
of circular dependencies.

src/ol/map.js

@@ -42,6 +42,7 @@ goog.require('ol.ObjectEventType');
 goog.require('ol.Pixel');
 goog.require('ol.PostRenderFunction');
 goog.require('ol.PreRenderFunction');
+goog.require('ol.RendererType');
 goog.require('ol.Size');
 goog.require('ol.Tile');
 goog.require('ol.TileQueue');
@@ -98,18 +99,6 @@ ol.OL3_LOGO_URL = 'data:image/png;base64,' +
     'q82CM2MwKeibqAvSO7MCABq0wXEPiqWEAAAAAElFTkSuQmCC';
 
 
-/**
- * Available renderers: `'canvas'`, `'dom'` or `'webgl'`.
- * @enum {string}
- * @todo api
- */
-ol.RendererType = {
-  CANVAS: 'canvas',
-  DOM: 'dom',
-  WEBGL: 'webgl'
-};
-
-
 /**
  * @type {Array.<ol.RendererType>}
  */