Temporarily disable loading of the downloads module in FF26.

nsIDownloadManager has been removed so the module needs updating to utilise the
replacement Downloads.jsm.

common/modules/config.jsm

@@ -45,6 +45,9 @@ var ConfigBase = Class("ConfigBase", {
      * initialization code. Must call superclass's init function.
      */
     init: function init() {
+        if (config.haveGecko("26"))
+            this.modules.global = this.modules.global.filter(m => m != "downloads"); // FIXME
+
         this.loadConfig();
 
         this.features.push = deprecated("Set.add", function push(feature) Set.add(this, feature));