move Layer.OSM in its own script file

lib/OpenLayers/Layer/OSM.js

@@ -0,0 +1,41 @@
+/* Copyright (c) 2006-2012 by OpenLayers Contributors (see authors.txt for 
+ * full list of contributors). Published under the Clear BSD license.  
+ * See http://svn.openlayers.org/trunk/openlayers/license.txt for the
+ * full text of the license. */
+
+/**
+ * @requires OpenLayers/Layer/XYZ.js
+ */
+
+/**
+ * Class: OpenLayers.Layer.OSM
+ * A class to access OpenStreetMap tiles. By default, uses the OpenStreetMap
+ *    hosted tile.openstreetmap.org 'Mapnik' tileset. If you wish to use
+ *    tiles@home / osmarender layer instead, you can pass a layer like:
+ * 
+ * (code)
+ *     new OpenLayers.Layer.OSM("t@h", 
+ *       "http://tah.openstreetmap.org/Tiles/tile/${z}/${x}/${y}.png"); 
+ * (end)
+ *
+ * This layer defaults to Spherical Mercator.
+ * 
+ * Inherits from:
+ *  - <OpenLayers.Layer.XYZ>
+ */
+OpenLayers.Layer.OSM = OpenLayers.Class(OpenLayers.Layer.XYZ, {
+     name: "OpenStreetMap",
+     attribution: "Data CC-By-SA by <a href='http://openstreetmap.org/'>OpenStreetMap</a>",
+     sphericalMercator: true,
+     url: 'http://tile.openstreetmap.org/${z}/${x}/${y}.png',
+     clone: function(obj) {
+         if (obj == null) {
+             obj = new OpenLayers.Layer.OSM(
+                 this.name, this.url, this.getOptions());
+         }
+         obj = OpenLayers.Layer.XYZ.prototype.clone.apply(this, [obj]);
+         return obj;
+     },
+     wrapDateLine: true,
+     CLASS_NAME: "OpenLayers.Layer.OSM"
+});