OpenStreetMap to OSM renaming

OSM is a well-known name, and is shorter than OpenStreetMap.

examples/mouse-position.js

@@ -5,7 +5,7 @@ goog.require('ol.control.MousePosition');
 goog.require('ol.control.defaults');
 goog.require('ol.coordinate');
 goog.require('ol.layer.TileLayer');
-goog.require('ol.source.OpenStreetMap');
+goog.require('ol.source.OSM');
 
 
 var map = new ol.Map({
@@ -19,7 +19,7 @@ var map = new ol.Map({
   ]),
   layers: [
     new ol.layer.TileLayer({
-      source: new ol.source.OpenStreetMap()
+      source: new ol.source.OSM()
     })
   ],
   renderers: ol.RendererHints.createFromQueryData(),