Use FileSystem API to store data in Opera

lib/filesystem/io.js

 /*
  * This file is part of Adblock Plus <http://adblockplus.org/>,
  * Copyright (C) 2006-2013 Eyeo GmbH
  *
  * Adblock Plus is free software: you can redistribute it and/or modify
  * it under the terms of the GNU General Public License version 3 as
  * published by the Free Software Foundation.
  *
  * Adblock Plus is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
@@ skipping 56 matching lines @@
 
     if ("spec" in file && /^defaults\b/.test(file.spec))
     {
       // Code attempts to read the default patterns.ini, we don't have that.
       // Make sure to execute first-run actions instead.
       var Utils = require("utils").Utils;
       Utils.runAsync(function()
       {
         if (localStorage.currentVersion)
           seenDataCorruption = true;
+        delete localStorage.currentVersion;
         callback(null);
       });
       return;
     }
 
     this._getFileEntry(file, false, function(fs, fileEntry)
     {
       fileEntry.file(function(file)
       {
         var reader = new FileReader();
@@ skipping 120 matching lines @@
         callback(null, {
           exists: true,
           isDirectory: fileEntry.isDirectory,
           isFile: fileEntry.isFile,
           lastModified: metadata.modificationTime.getTime()
         });
       }, callback);
     }, callback);
   }
 };