Use FileSystem API to store data in Opera

lib/websql/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 44 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;
     }
 
     var path = this._getFilePath(file);
     var runAsync = require("utils").Utils.runAsync;
 
     this._transaction(function(tx)
     {
@@ skipping 114 matching lines @@
               exists: true,
               isDirectory: false,
               isFile: true,
               lastModified: results.rows.item(0).last_modified
             });
         }
       );
     });
   }
 };