make available as OC.Backbone to avoid conflicts

core/js/oc-backbone.js

+/*
+ * Copyright (c) 2015
+ *
+ * This file is licensed under the Affero General Public License version 3
+ * or later.
+ *
+ * See the COPYING-README file.
+ *
+ */
+if(!_.isUndefined(Backbone)) {
+	OC.Backbone = Backbone.noConflict();
+}

lib/private/util.php

@@ -455,6 +455,11 @@ class OC_Util {
 		$path = OC_Util::generatePath($application, 'vendor', $file);
 		if (!in_array($path, self::$scripts)) {
 			self::$scripts[] = $path;
+			if($file === 'backbone/backbone') {
+				// makes backbone available as OC.Backbone in order to avoid
+				// conflicts, because apps (like Mail) may bring own versions
+				OC_Util::addScript('oc-backbone');
+			}
 		}
 	}